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Question 1 of 20 · Earth and its system components
A Stream Table Model
A class used a stream table, a long tray filled with a mix of sand and gravel, to model how running water shapes land. Each time, they poured 2 liters of water in at the top end over 1 minute. They changed only the slope of the tray. Sediment that washed out of the bottom end was caught, dried and weighed. Each slope was tested three times, and the table shows the mean.
Slope of tray
5°
10°
15°
20°
Mean dry sediment carried out (g)
40
95
160
240
The students also saw that where the water spread into a pool at the bottom end, it slowed down. Gravel settled first, close to where the water entered the pool, and fine sand settled farther out.
Weathering breaks rock into smaller pieces but does not move them. Erosion is the removal and transport of rock and soil by water, wind or ice. Deposition is the dropping of sediment when the water, wind or ice slows down.
Which statement best describes the result of the stream table experiment?
Hint
Read the table from left to right. What happens to the sediment as the slope gets steeper?
Step-by-step solution
Where the answer comes from: the table shows mean sediment carried out of the tray: 40 g at 5°, 95 g at 10°, 160 g at 15° and 240 g at 20°.
Step by step:
The slope (independent variable) goes up from 5° to 20°.
The sediment carried out (dependent variable) goes up every time: 40 → 95 → 160 → 240 g.
A steeper slope makes water flow faster, and faster water can pick up and carry more sediment. That is more erosion.
The answer is as the slope increased, the amount of sediment the water eroded and carried out increased.
Check: The increase gets bigger at each step (55 g, then 65 g, then 80 g), so the effect grows stronger at steeper slopes. Nothing in the data shows it leveling off ✓.
Tip: Describe a relationship by naming both variables and the direction: as X increased, Y increased.
Question 2 of 20 · Earth and its system components
A Chain of Volcanic Islands
Some volcanoes form far from plate boundaries, above a hot spot: a plume of unusually hot rock rising from deep in the mantle. The hot spot stays in about the same place while the tectonic plate above it slowly moves. As the plate carries a volcano away from the hot spot, that volcano stops erupting and a new one forms over the plume. Over millions of years, this builds a chain of islands that get older in the direction the plate is moving. Older islands also sink and wear away, so they become lower. The Hawaiian Islands formed this way.
The table describes a fictional island chain in the Pacific Ocean. Islands farther from the hot spot lie farther to the northwest. Distances are measured from Island V, the active volcano over the hot spot.
Island
Distance from hot spot (km)
Age of oldest rock (million years)
Highest point (m)
V
0
0 (still erupting)
4,100
W
160
2.0
3,000
X
320
4.0
1,200
Y
480
6.0
400
Z
640
8.0
5 (coral reef only)
Why are the islands in the chain older toward the northwest?
Hint
Which part stays in place, the hot spot or the plate?
Step-by-step solution
Where the answer comes from: the passage says "The hot spot stays in about the same place while the tectonic plate above it slowly moves," building a chain of islands "that get older in the direction the plate is moving." It also says islands farther from the hot spot "lie farther to the northwest."
Step by step:
A new volcano always forms over the fixed hot spot (Island V today).
The plate carries each finished island away from the hot spot.
The longer ago an island formed, the farther it has been carried.
The older islands lie to the northwest, so the plate must be moving toward the northwest.
The answer is the plate is moving northwest over a hot spot that stays in place.
Check: If the hot spot moved northwest under a still plate, the newest island would be in the northwest, the opposite of the data ✓.
Tip: In hot-spot questions, the youngest island marks the hot spot, and the line of older islands points the way the plate is going.
Question 3 of 20 · Structure of the cosmos
Fill inSpring and Neap Tides at Gull Point
The Moon's gravity pulls on Earth's oceans and raises two bulges of water, one on the side facing the Moon and one on the opposite side. The Sun's gravity raises smaller bulges. When the Sun, Earth and Moon line up, at new moon and full moon, the bulges add together. This gives spring tides, with the highest highs, the lowest lows and the largest tidal range. When the Moon is at a right angle to the Sun–Earth line, at first quarter and third quarter, the Sun's pull partly cancels the Moon's. This gives neap tides, with the smallest range. (Spring tides have nothing to do with the season of spring.) The tidal range is the high-tide height minus the low-tide height.
Tide table for Gull Point, a fictional harbor. Heights are in meters above the average low-water level, so a negative height is lower than usual.
Date
Moon phase
Highest high tide (m)
Lowest low tide (m)
March 3
Third quarter
1.8
0.6
March 10
New moon
2.6
−0.2
March 17
First quarter
1.7
0.7
March 25
Full moon
2.5
−0.1
Using the tide table, what was the tidal range at Gull Point on March 10?
meters
Type your answer in the box. Fractions like 3/4 are fine.
Hint
Range = high − low. Subtracting a negative number is the same as adding.
Step-by-step solution
Where the answer comes from: the table row "| March 10 | New moon | 2.6 | −0.2 |" and the passage's definition: "The tidal range is the high-tide height minus the low-tide height."
Step by step:
High tide on March 10: 2.6 m. Low tide: −0.2 m (below the average low-water level).
Range = high − low:
2.6 - (-0.2) = 2.6 + 0.2 = 2.8 \text{ m}
The tidal range on March 10 was 2.8 meters.
Check: Picture a number line. From −0.2 up to 0 is 0.2 m, and from 0 up to 2.6 is 2.6 m. Total 0.2 + 2.6 = 2.8 m ✓. A range of 2.4 m would come from ignoring the minus sign.
Tip: When a low value is negative, the range is larger than the high value. Write the subtraction with parentheses so you do not lose the sign.
Question 4 of 20 · Life functions and energy intake
Algae and Carbon Dioxide
Photosynthesis needs light, water, and carbon dioxide (CO₂). When one of these is in short supply, it limits how fast photosynthesis can go, even if the others are plentiful. A factor that holds back the rate in this way is called a limiting factor. Temperature also matters, because the reactions of photosynthesis are controlled by enzymes, which work more slowly when they are cool.
A biology class put the same amount of green algae into 12 sealed flasks of water under the same bright light. They added different amounts of dissolved CO₂ to the flasks. Six flasks were kept at 15 °C and six at 25 °C. The class measured how much oxygen the algae released in one hour.
Which statement best describes the results for the algae kept at 25 °C?
Hint
Follow the solid blue line from left to right. Does it keep climbing at the same pace the whole way?
Step-by-step solution
Evidence: the 25 °C line reads 0, 12, 20, 25, 26, 26 mg per hour at 0, 5, 10, 15, 20, and 25 mg/L of CO₂.
Step by step:
From 0 to 15 mg/L, oxygen output climbs quickly: 0 → 12 → 20 → 25.
From 15 to 25 mg/L, it barely changes: 25 → 26 → 26. The line levels off.
So adding CO₂ sped up photosynthesis at first, but above about 15 to 20 mg/L, more CO₂ made little difference. Something else, such as light or temperature, became the limiting factor.
Eliminate B (the rise did not continue at a steady rate), C (output went up, not down), and D (the line changed a lot at low CO₂).
The answer is A.
Tip: a curve that rises and then flattens means the factor on the x-axis stopped being the one that limits the rate.
Question 5 of 20 · Energy flow in ecosystems
Fill inEnergy in a Grassland
Ecologists estimated how much energy was stored in each trophic level of a grassland in one year. Energy is given in kilojoules per square meter (kJ/m²). Producers capture only about 1% of the sunlight energy that reaches them. After that, only about 10% of the energy at one trophic level becomes part of the next level; the rest is used for life processes and lost as heat, or stays in parts that are not eaten.
Trophic level
Example organisms
Energy stored (kJ/m² per year)
Producers
grasses, wildflowers
25,000
Primary consumers
grasshoppers, mice
2,500
Secondary consumers
spiders, snakes
250
Tertiary consumers
hawks
?
According to the passage, producers capture only about 1% of the sunlight energy that reaches them. About how much sunlight energy reached the producers in this grassland during the year?
kJ/m²
Type your answer in the box. Fractions like 3/4 are fine.
Hint
The producers' 25,000 kJ/m² is 1% of the sunlight. What number has 25,000 as its 1%?
Step-by-step solution
Evidence: the passage says "Producers capture only about 1% of the sunlight energy that reaches them," and the table shows the producers stored 25,000 kJ/m².
Step by step:
Let S be the sunlight energy. Then 0.01 \times S = 25{,}000.
A common slip is multiplying by 0.01 (25{,}000 \times 0.01 = 250), which goes the wrong way: the sunlight must be much larger than what the plants capture.
The answer is 2,500,000 kJ/m².
Check: 1% of 2,500,000 is 2{,}500{,}000 \div 100 = 25{,}000 ✓
Tip: when you know the part and the percent, divide the part by the percent (as a decimal) to find the whole. The whole should be bigger than the part.
Question 6 of 20 · Heredity and genetics
Fill inGuinea Pig Coat Color
In guinea pigs, one gene controls coat color. The allele for a black coat (B) is dominant over the allele for a white coat (b).
A breeder made three crosses. For each pair of parents, she recorded the coat colors of all the offspring they produced over several litters.
Cross
Parent 1
Parent 2
Black offspring
White offspring
1
Black
White
12
0
2
Black
White
7
6
3
Black
Black
15
5
The black parent in Cross 2 is heterozygous (Bb). If it is mated with a different white guinea pig, what is the probability that any one offspring will be white?
Enter your answer as a percent. %
Type your answer in the box. Fractions like 3/4 are fine.
Hint
What is the genotype of any white guinea pig? Set up a Punnett square for Bb × that genotype.
Step-by-step solution
Where the answer comes from: the passage says black (B) is dominant over white (b), so every white guinea pig is bb. The black parent is given as Bb.
Step by step:
Cross: Bb × bb.
Punnett square:
B
b
b
Bb
bb
b
Bb
bb
Two of the four boxes are bb (white): \dfrac{2}{4} = \dfrac{1}{2} = 50\%.
Answer: 50%.
Check: Cross 2 in the table (also Bb × white) gave 7 black and 6 white offspring, close to the 1 : 1 ratio that 50% predicts ✓
Tip: a cross between a heterozygote and a homozygous recessive always gives a 1 : 1 ratio, 50% of each phenotype.
Question 7 of 20 · Heredity and genetics
The DNA Ladder
DNA is shaped like a twisted ladder, called a double helix. The sides of the ladder are made of sugar and phosphate. Each rung is a pair of bases. There are four bases: adenine (A), thymine (T), cytosine (C) and guanine (G).
The bases always pair the same way: A pairs with T, and C pairs with G. Because of this rule, the two strands are complementary: the order of bases on one strand sets the order on the other. When a cell copies its DNA, the two strands separate, and each strand serves as a pattern for building a new partner strand.
Because every A is paired with a T and every C is paired with a G, a double-stranded DNA molecule always contains equal amounts of A and T, and equal amounts of C and G.
One strand of a DNA molecule has the base sequence A T G C C A. Which sequence is on the complementary strand?
Hint
Use the pairing rule from the passage for each base, one at a time.
Step-by-step solution
Where the answer comes from: the passage states the pairing rule: "A pairs with T, and C pairs with G."
Step by step: pair each base in order.
Given strand
A
T
G
C
C
A
Partner
T
A
C
G
G
T
Answer: T A C G G T.
Check: pair the answer back with the original: A–T, T–A, G–C, C–G, C–G, A–T. Every rung is an A-T or C-G pair ✓
Why the traps fail: U (uracil) is found in RNA, not DNA; copying the same sequence ignores the pairing rule; pairing A with G and T with C breaks the rule.
Tip: remember the pairs by shape of the letters: the straight-line letters A and T go together, and the curvy letters C and G go together.
Question 8 of 20 · Evolution
Beaks After a Drought
On a small island, a population of seed-eating birds called ground finches varies in beak depth (how tall the beak is from top to bottom). Beak depth is largely inherited: parents with deep beaks tend to have offspring with deep beaks. Birds with deeper beaks can crack larger, harder seeds.
One year, a severe drought struck the island. Plants that make small, soft seeds died back, and most of the food left was large, hard seeds. Many finches died during the drought. Researchers measured the beaks of the birds before the drought, of the birds that survived it, and of the offspring hatched the year after.
Group
Average beak depth (mm)
Birds before the drought
9.4
Birds that survived the drought
9.9
Offspring hatched after the drought
9.8
A student writes: "During the drought, each finch grew a deeper beak because it needed to crack the hard seeds." Which statement best explains the error in the student's reasoning?
Hint
Look at the table: did the change show up because individual beaks grew, or because the mix of birds changed?
Step-by-step solution
Where the answer comes from: the passage says "Many finches died during the drought" and the table shows that the survivors averaged 9.9 mm, compared with 9.4 mm before. Beak depth "is largely inherited."
Step by step:
The student describes individual birds changing their bodies because of a need. That is not how inherited traits change.
What actually happened: birds that already had deeper beaks were more likely to survive; many shallow-beaked birds died.
The survivors' average was higher because of who survived, not because any bird's beak grew. Their offspring inherited deep beaks.
Answer: Individual finches do not change their inherited traits because of need; the average changed because finches that already had deeper beaks survived and reproduced.
Check: even if a bird's beak did wear or grow during its life, such changes are not stored in its DNA, so they would not be passed to its offspring.
Tip: watch for the words needed to, in order to, or tried to in an explanation of evolution. They usually signal the need-based (Lamarckian) error.
Question 9 of 20 · Energy: conservation, transformation, flow
Fill inComparing Light Bulbs
A hardware store tested three bulbs that give off the same amount of light. For each bulb, the table shows how much electrical energy goes into the bulb each second and how much of it comes out as light each second. All of the energy that does not come out as light becomes thermal energy, which is why some bulbs get hot.
Bulb type
Electrical energy in each second (J)
Light energy out each second (J)
Incandescent
60
3
Compact fluorescent (CFL)
15
3
LED
10
3
The efficiency of a device tells what percent of the energy put in comes out in the useful form:
\text{efficiency} = \frac{\text{useful energy out}}{\text{total energy in}} \times 100\%
Use the table and the efficiency formula in the passage.
What is the efficiency of the LED bulb?
%
Type your answer in the box. Fractions like 3/4 are fine.
Hint
Useful energy out goes on top of the fraction; total energy in goes on the bottom.
Step-by-step solution
Evidence: The table shows the LED bulb uses 10 J of electrical energy each second and gives out 3 J of light energy each second. Light is the useful output of a bulb.
Step by step:
Write the formula: \text{efficiency} = \dfrac{\text{useful energy out}}{\text{total energy in}} \times 100\%.
Check: An efficiency must be between 0% and 100%. Dividing the other way (10 \div 3) would give 333%, which is impossible because no device puts out more energy than it takes in.
Tip: Efficiency is always useful out over total in. If your answer is above 100%, you divided upside down.
Question 10 of 20 · Chemical properties and reactions
How Temperature Affects Solubility
Solubility is the greatest amount of a substance (the solute) that can dissolve in a given amount of solvent at a given temperature. A solution holding exactly that maximum is saturated. A solution holding less than the maximum is unsaturated, so more solute can still dissolve. If a saturated solution is cooled and the solubility drops, the extra solute comes out of the solution as solid crystals.
The graph shows how many grams of two salts can dissolve in 100 g of water at different temperatures.
Potassium nitrate is used in fertilizers. Sodium chloride is ordinary table salt. For most solid solutes, solubility increases as the water gets warmer, but the amount of increase is very different from one substance to another.
A student adds 50 g of potassium nitrate to one beaker and 50 g of sodium chloride to another. Each beaker holds 100 g of water at 40 °C. She stirs both until no more will dissolve.
Which result does the graph predict?
Hint
Read each salt's solubility at 40 °C and compare it with 50 g.
Step-by-step solution
Evidence: On the graph at 40 °C, potassium nitrate's solubility is 64 g and sodium chloride's is 36 g per 100 g of water. The passage explains that a solution holding "less than the maximum is unsaturated."
Step by step:
Potassium nitrate: 50 g added, maximum 64 g. Since 50 < 64, all of it dissolves, and the solution is unsaturated (14 g more could still dissolve).
Sodium chloride: 50 g added, maximum 36 g. Only 36 g dissolves, so 50 - 36 = 14 g stays undissolved at the bottom, and the solution is saturated.
Note the trap: at 0 °C sodium chloride is more soluble than potassium nitrate, but by 40 °C the order has switched.
The answer is All of the potassium nitrate dissolves, but about 14 g of sodium chloride stays undissolved.
Tip: For "will it all dissolve?" questions, compare the amount added with the solubility at that exact temperature. More than the maximum means leftover solid.
Question 11 of 20 · Chemical properties and reactions
Fill inA Tower of Liquids
A student measured the mass and volume of four household liquids. Then she slowly and carefully poured the samples, one at a time, into a tall clear cylinder. The liquids did not mix right away and formed four separate layers. A liquid that is less dense floats on top of a liquid that is denser.
Liquid
Mass (g)
Volume (mL)
Honey
28.4
20.0
Dish soap
31.8
30.0
Water
40.0
40.0
Vegetable oil
23.0
25.0
Density is mass divided by volume: D = \dfrac{m}{V}. (1 mL = 1 cm³.)
The student wants to know whether dish soap is denser than water. From the mass and volume in the table, calculate the density of the dish soap.
g/mL
Type your answer in the box. Fractions like 3/4 are fine.
Hint
Divide the dish soap's mass by its volume.
Step-by-step solution
Evidence: The table lists dish soap with a mass of 31.8 g and a volume of 30.0 mL. The passage gives D = \dfrac{m}{V}.
Step by step:
Mass on top, volume on the bottom:
D = \frac{31.8\text{ g}}{30.0\text{ mL}} = 1.06\text{ g/mL}
The units are grams per milliliter, which is the same as g/cm³ because 1 mL = 1 cm³.
The dish soap's density is 1.06 g/mL.
Check: Dish soap's mass (31.8 g) is a bit more than its volume (30.0 mL), so its density should be a bit more than 1. ✓ Dividing the other way gives 0.94, which would wrongly suggest soap floats on water.
Tip: A quick reality check for density: if the mass number is bigger than the volume number, the density is greater than 1 (denser than water).
Question 12 of 20 · Chemical properties and reactions
Testing Garden Soil
Different plants grow best in soil with different pH values. A community garden posted this chart for its members.
Plant
Soil pH the plant prefers
Blueberries
4.5 to 5.5
Potatoes
5.0 to 6.0
Tomatoes
6.0 to 6.8
Asparagus
6.5 to 7.5
Lilacs
7.0 to 8.0
A pH of 7 is neutral; a pH below 7 is acidic and a pH above 7 is basic. The pH scale is logarithmic: each drop of one pH unit means the soil is 10 times more acidic. Garden lime (calcium carbonate) is a base, so mixing it into soil neutralizes some of the acid and raises the pH. Garden sulfur slowly forms an acid in moist soil and lowers the pH.
Ana tested the soil in her plot. Its pH was 4.8.
Which statement about Ana's soil is correct?
Hint
Compare 4.8 with 7, then check which plant's range includes 4.8.
Step-by-step solution
Evidence: The passage says "a pH below 7 is acidic" and that Ana's soil pH "was 4.8." The chart lists blueberries at "4.5 to 5.5" and potatoes at "5.0 to 6.0."
Step by step:
Classify:4.8 < 7, so the soil is acidic, not basic or neutral.
Match a plant: 4.8 is inside the blueberry range (4.5 to 5.5). It is just below the potato range, which starts at 5.0, and far below tomatoes (6.0 to 6.8) and lilacs (7.0 to 8.0).
The answer is The soil is acidic, and it suits blueberries without any change.
Check: Blueberries are well known as acid-loving plants, which fits.
Tip: On the pH scale, low numbers are acidic, 7 is neutral and high numbers are basic. A lower number means more acidic, not less.
Question 13 of 20 · Comprehending scientific presentations
A Model of Blood Circulation
The heart is a muscular pump with two sides. The diagram is a simplified model of the path blood takes through the human body. Each arrow shows the direction in which blood flows. The key explains the two kinds of arrows.
Blood picks up oxygen in the lungs. Body tissues, such as muscles, use that oxygen for energy, so blood returning from the tissues carries little oxygen. In this model, the right side of the heart pumps blood only to the lungs, and the left side pumps blood to the rest of the body.
According to the diagram, where does blood travel immediately after it leaves the lungs?
Hint
Put your finger on the Lungs box and follow the arrow that points away from it.
Step-by-step solution
In this model every arrow points in the direction blood flows, so follow the arrow that leaves the Lungs box.
Step by step:
Two arrows touch the Lungs box. The blue arrow from the right side of the heart points into the lungs.
The dashed red arrow starts at the lungs and points down into the Left side of heart box.
So blood goes from the lungs straight to the left side of the heart. The key says this blood is oxygen-rich, which matches the passage: 'Blood picks up oxygen in the lungs.'
The correct answer is A, the left side of the heart.
Check: Body tissues come next, but only after the left side of the heart pumps the blood. The right side of the heart sends blood to the lungs; it does not receive blood from them.
Tip: In any flow model, follow arrows one link at a time. 'Immediately after' means the very next box, not one further along the path.
Question 14 of 20 · Reasoning from data
Ice Cream and Sunburn
A city health department compared two sets of data for each month of one year: the number of ice cream cones sold in the city (in thousands) and the number of people treated at city clinics for sunburn. Each point on the scatter plot represents one month.
A local newspaper reported the data under the headline "Is ice cream causing sunburns?"
Which factor most likely explains why ice cream sales and sunburn cases rise and fall together?
Hint
Think of something that would make people buy more ice cream AND spend more time in strong sun.
Step-by-step solution
When two variables rise and fall together but neither causes the other, a third variable may be causing both. The plot has one point per month, which hints at seasons.
Step by step:
Hot, sunny months make people want cold treats, so ice cream sales go up.
The same hot, sunny months mean more time outdoors in strong sunlight, so sunburns go up.
So sunny, warm weather (choice D) explains both trends.
Choice A (price of ice cream) might affect sales but has no link to sunburn. Choice B (number of clinics) might affect how many people are treated but not ice cream sales. Choice C (flavors) affects neither sunburn nor the seasonal pattern.
The correct answer is D.
Tip: For any correlation, ask: "Is there a hidden factor that could drive both?" Weather, age, population size and time are common hidden factors.
Question 15 of 20 · Evaluating conclusions with evidence
What Causes the Seasons?
A student claims: "Summer happens when Earth is closest to the Sun, and winter happens when Earth is farthest away."
Earth's orbit around the Sun is nearly a circle. Its distance from the Sun changes only slightly during the year.
Time of year
Earth–Sun distance (million km)
Early January (closest)
147.1
Early July (farthest)
152.1
The table below shows average monthly temperatures for two fictional cities at similar distances from the equator. Northville is in the Northern Hemisphere, and Southport is in the Southern Hemisphere.
City
Average January temperature (°C)
Average July temperature (°C)
Northville
−3
23
Southport
24
10
Which claim is NOT supported by the data in the passage?
Hint
Three choices restate numbers from the tables. Check the remaining one against Northville's January temperature.
Step-by-step solution
Check each choice against the two tables.
Evidence: Earth is 147.1 million km from the Sun in early January (closest) and 152.1 million km in early July (farthest). Northville: −3 °C in January, 23 °C in July. Southport: 24 °C in January, 10 °C in July.
Step by step:
"Earth is closer to the Sun in January than in July" — 147.1 < 152.1. Supported.
"Northville is warmer in July than in January" — 23 > −3. Supported.
"When Northville has its warm season, Southport has its cool season" — in July, Northville is 23 °C while Southport is 10 °C. Supported.
"Earth's closest approach to the Sun causes summer everywhere on Earth" — in January, when Earth is closest, Northville averages −3 °C. Not supported.
The correct answer is Earth's closest approach to the Sun causes summer everywhere on Earth.
Check: If closeness caused summer for everyone, both cities would be warm in January. Only Southport is.
Tip: A claim about everywhere or all fails with a single counterexample — here, one cold city during closest approach.
Question 16 of 20 · Expressing scientific information
Select allHow Often Earthquakes Happen
Seismologists sort earthquakes by magnitude, a number that describes how much energy an earthquake releases. The table shows the average number of earthquakes recorded worldwide each year in four magnitude ranges, based on many years of records.
Magnitude range
Average number per year
5.0–5.9
1,300
6.0–6.9
130
7.0–7.9
15
8.0 and higher
1
Each step up of 1.0 in magnitude means an earthquake releases about 32 times as much energy.
Select all the statements that accurately describe the information in the passage.
Select all that apply.
Hint
Check each statement with a quick calculation. For energy, remember the factor is multiplied for each step of 1.0.
Step-by-step solution
Where the answer comes from: the table ("| 5.0–5.9 | 1,300 |", "| 6.0–6.9 | 130 |", "| 7.0–7.9 | 15 |") and the sentence "Each step up of 1.0 in magnitude means an earthquake releases about 32 times as much energy."
Step by step:
A — accurate.1{,}300 \div 130 = 10, so magnitude 5 earthquakes are about 10 times as common.
B — accurate. The table gives 15 per year for 7.0–7.9.
C — not accurate. From 6.0 to 8.0 is two steps: 32 \times 32 = 1{,}024, about 1,000 times as much energy, not 2 times.
D — accurate. One step from 6.0 to 7.0 means about 32 times as much energy.
E — not accurate. Magnitude 6.0 or higher: 130 + 15 + 1 = 146 out of 1{,}300 + 146 = 1{,}446, about 10%, not more than half.
Correct answers: A, B and D.
Check: for multi-step energy questions, multiply the factor once per step; never add the steps.
Tip: In select-all questions, verify each statement on its own with the data; numbers that look familiar can still be used the wrong way.
Question 17 of 20 · Scientific theories
Fill inTiming Earthquake Waves
When an earthquake happens, it sends out two main kinds of waves through rock. P-waves (primary waves) are faster and arrive at a seismic station first. S-waves (secondary waves) are slower and arrive later.
In the crust of one region, seismologists use these average speeds:
Wave
Average speed in the crust
P-wave
6.0 km/s
S-wave
3.5 km/s
The time a wave takes to reach a station is found with
t = \dfrac{d}{v}
where t is travel time in seconds, d is distance in kilometers, and v is the wave's speed in km/s.
Because the two waves travel at different speeds, the gap between the P-wave arrival and the S-wave arrival grows the farther a station is from the earthquake. Seismologists use this S–P time gap to work out how far away an earthquake was, even when they do not know exactly when it began.
A seismic station is 210 km from an earthquake. Using the formula and the speeds in the passage, how many seconds after the earthquake does the P-wave reach the station?
s
Type your answer in the box. Fractions like 3/4 are fine.
Hint
Use the P-wave speed, not the S-wave speed, and divide distance by speed.
Step-by-step solution
Where the answer comes from: the passage gives the formula t = \dfrac{d}{v} and the table gives the P-wave speed as 6.0 km/s. The station is 210 km away.
Step by step:
Choose the right speed: the question asks about the P-wave, so v = 6.0 km/s.
Substitute: t = \dfrac{210\text{ km}}{6.0\text{ km/s}}.
Divide: 210 \div 6.0 = 35.
Units: km divided by km/s leaves seconds.
Correct answer: 35 s.
Check:35\text{ s} \times 6.0\text{ km/s} = 210 km ✓. (Using the S-wave speed by mistake would give 210 \div 3.5 = 60 s, which is when the S-wave arrives.)
Tip: Before you calculate, circle which row of the table the question is about. Many GED formula questions give two similar values so you must pick the right one.
Question 18 of 20 · Energy: conservation, transformation, flow
A solar garden light has a small solar panel on top and a rechargeable battery inside. During the day, sunlight striking the panel charges the battery. At night, the battery powers a small bulb that glows.
Which sequence correctly shows the energy transformations, from morning to night?
Hint
The energy has to be stored somewhere between day and night. What kind of energy does a charged battery hold?
Step-by-step solution
Evidence: The stem says sunlight "charges the battery" in the day and "the battery powers a small bulb" at night. Energy must be stored in between.
Step by step:
Daytime: the panel absorbs light (radiant) energy and turns it into electrical energy.
Storage: charging the battery drives chemical reactions inside it, so the energy is stored as chemical energy.
Night: the battery's chemical energy is turned back into electrical energy in the circuit.
Output: the bulb turns electrical energy into light energy (plus a little thermal energy).
The answer is light → electrical → chemical → electrical → light.
Check: Every step has a cause in the story: panel, charging, battery, bulb. No step is skipped, and the chain begins and ends with light.
Tip: When a device stores energy for later (batteries, food, fuel), look for chemical energy in the middle of the chain.
Question 19 of 20 · Organization of life: cells, tissues, organisms
Drop-down
Select the words that correctly complete this summary of the cell theory.
All living things are made of one or more . The cell is the basic unit of . All cells come from .
Choose an answer from each menu.
Hint
The cell theory has three parts, and the third part disproved the old idea that life can arise from nonliving things.
Step-by-step solution
The cell theory is one of the foundational theories of biology. It was developed in the 1800s as microscopes improved:
Matthias Schleiden (1838) concluded that plants are made of cells, and Theodor Schwann (1839) concluded the same for animals.
Rudolf Virchow (1855) added that every cell comes from a cell that existed before it.
The three parts:
All living things are made of one or more cells. (Bacteria are one cell; a person is trillions.)
The cell is the basic unit of structure and function in living things: the smallest unit that can carry out all life processes.
All cells come from pre-existing cells, by cell division.
Why the wrong items fail: atoms make up everything, living or not, so they do not define life. Tissues exist only in multicellular organisms, so a one-celled bacterium has none. The idea that cells arise from mud or dust is spontaneous generation, which experiments in the 1800s disproved.
Answer: cells; structure and function in living things; pre-existing cells.
Tip: a scientific theory is a well-tested explanation supported by much evidence, not a guess. GED questions may ask which observation supports one part of a theory.
Question 20 of 20 · Chemical properties and reactions
Drop-down
A thin, protective coating forms on aluminum pans when aluminum reacts with oxygen in the air to form aluminum oxide.
Select the coefficients that balance the equation.
Al + \text{O}_2 → \text{Al}_2\text{O}_3
Choose an answer from each menu.
Hint
Oxygen atoms come in 2s on the left and in 3s on the right. Find the smallest number of oxygen atoms that both can make.
Step-by-step solution
Evidence: The formula \text{Al}_2\text{O}_3 has 2 aluminum atoms and 3 oxygen atoms. \text{O}_2 has 2 oxygen atoms. By the law of conservation of mass, each kind of atom must be equal on both sides.
Step by step:
Oxygen first: the left side has oxygen in pairs (\text{O}_2) and the right side in threes (\text{Al}_2\text{O}_3). The smallest number both can make is 6.
To get 6 O on the right: 2\,\text{Al}_2\text{O}_3 (2 \times 3 = 6). To get 6 O on the left: 3\,\text{O}_2 (3 \times 2 = 6).
Aluminum:2\,\text{Al}_2\text{O}_3 contains 2 \times 2 = 4 Al, so put 4 in front of Al.
Final equation:
4\,\text{Al} + 3\,\text{O}_2 \rightarrow 2\,\text{Al}_2\text{O}_3
Atom
Left
Right
Al
4
2 × 2 = 4
O
3 × 2 = 6
2 × 3 = 6
The coefficients are 4, 3 and 2.
Check: The coefficients 4, 3, 2 have no common factor, so this is the simplest balanced form.
Tip: When an element has an even subscript on one side and an odd one on the other (2 and 3 here), use the least common multiple (6) to balance it, then fix the other element.