Comparing Data Across Multiple Figures — ACT Science

Introduction

ACT Science passages rarely give you one figure. They give you three. Students who can connect Figure 1 to Figure 3 in seconds score in the 30s. Students who read each figure in isolation get stuck.

Multi-figure comparison questions appear in nearly every ACT Science passage — roughly 20–25% of the test. These follow a completely learnable two-step pattern.

By the end of this lesson you will be able to:

Identify the bridge variable that links two separate figures in the same passage
Transfer a value from one figure to locate a corresponding value in a second figure
Recognize when figures show the same data at different scales or conditions

You will connect a table of enzyme activity to a separate graph of pH levels — two figures sharing one bridge variable — exactly the cross-figure hop ACT Science uses to separate high scorers.

The Concept

The Core Rule

Multi-figure questions always have a bridge variable — one quantity appearing in both figures. Find the bridge, transfer the value, read the answer. Never guess at connections not explicitly shown.

How the ACT tests this

Chain questions: read Figure 1 first, use that result as input for Table 2
Trend comparison: characterize direction in each figure, then compare
Condition matching: match labeled trial conditions across two different displays

Finding the Bridge Variable

Scan both figure titles and axis labels for a shared variable name — same name, same units. Common bridges: temperature, pH, concentration, time, trial number.

Scan both figures for shared variable names
Check if trial numbers in a table appear as axis labels in a graph
Confirm units match — °C vs K may require conversion awareness

The Two-Step Method

Step A: extract a value from the first figure and write it down. Step B: use that value as the lookup key in the second figure. Writing the intermediate value is essential — holding it in memory causes errors.

Step A: Read Figure X → write the intermediate value
Step B: Use that value to look up the answer in Figure Y
Ignore all figures not named in the question

Comparing Trends

Describe each figure's trend in one word (increasing/decreasing/peaked/flat) before comparing.

Both increasing = same trend
One increasing, one decreasing = opposite trends
One flat, one changing = one variable does not respond

Your strategy

Step 1 — Identify which two figures are referenced. Write their labels.
Step 2 — Find the bridge variable appearing in both figures.
Step 3 — Extract the intermediate value from the first figure. Write it down.
Step 4 — Use the intermediate value to look up the final answer in the second figure.

Worked Examples

Easy Example 1 Option D: Correct Species From Table 1, But Wrong Bar Read In Figure 1. Students Rush The Second Lookup After Solving The First Step Correctly.

Table 1 shows light intensity (lux) at maximum photosynthesis for three plant species. Figure 1 shows average leaf area (cm²) for the same three species.

Table 1: Species A=800 lux, B=1200 lux, C=500 lux. Figure 1: Bar graph — Species A=45 cm², B=30 cm², C=60 cm².

According to Table 1 and Figure 1, which species requires the highest light intensity and what is its average leaf area?

A. Species A; 45 cm²
B. Species B; 30 cm² (Correct answer)
C. Species C; 60 cm²
D. Species B; 60 cm²

Step 1

Step 1 — Bridge: Species label appears in both figures.

Step 2

Step 2 — Table 1: highest lux = Species B (1200). Write 'Species B'.

Step 3

Step 3 — Figure 1: Species B bar = 30 cm².

Step 4

Step 4 — Answer: Species B; 30 cm². Option B.

Correct answer: B

Why B is correct

Species B = 1200 lux (highest) and 30 cm² leaf area. Correct.

Why other options are wrong

A: Species A = 800 lux, not the highest. Incorrect.

C: Species C = 500 lux, the lowest. Incorrect.

D: Species B is right but 60 cm² is Species C's leaf area — wrong bar read. Incorrect.

⚠ Trap: Option D: correct species from Table 1, but wrong bar read in Figure 1. Students rush the second lookup after solving the first step correctly.

Medium Example 2 Answering 30% Because The Question Says '30°C' — Matching The Number Without Using Either Figure.

Figure 1: reaction rate (mol/s) vs. temperature (°C) for Catalyst X. Figure 2: product yield (%) vs. reaction rate (mol/s).

Figure 1: peaks at 30°C = 0.8 mol/s. Figure 2: linear — 0.8 mol/s → 80% yield.

Based on Figure 1 and Figure 2, what would be the expected product yield at 30°C?

A. 30%
B. 50%
C. 80% (Correct answer)
D. 100%

Step 1

Step 1 — Bridge: reaction rate (mol/s) is y-axis of Figure 1 and x-axis of Figure 2.

Step 2

Step 2 — Figure 1 at 30°C: rate = 0.8 mol/s. Write '0.8'.

Step 3

Step 3 — Figure 2 at 0.8 mol/s: yield = 80%.

Step 4

Step 4 — Answer: 80%. Option C.

Correct answer: C

Why C is correct

30°C → 0.8 mol/s → 80%. Correct.

Why other options are wrong

A: 30% = 0.3 mol/s in Figure 2, which is the rate at 50°C in Figure 1. Incorrect.

B: 50% = 0.5 mol/s = rate at 20°C. Misidentifying the temperature. Incorrect.

D: 100% requires 1.0 mol/s, never reached in Figure 1. Incorrect.

⚠ Trap: Answering 30% because the question says '30°C' — matching the number without using either figure.

Hard Example 3 Option D Exploits Axis-scale Confusion: Y-axis Goes To 20s And Students Glance At The Scale Top Instead Of Reading The Moon Data Point's Y-position At 18s.

Table 1 reports maximum height (m) of a projectile on three celestial bodies. Figure 1 is a scatter plot of time of flight (s) vs. maximum height (m).

Table 1: Moon=122m, Mars=54m, Earth=20m. Figure 1: Moon(122m, 18s), Mars(54m, 10s), Earth(20m, 4s). Linear upward trend.

According to Table 1 and Figure 1, on which body does the projectile have the longest time of flight, and what is that time?

A. Earth; 4 s
B. Mars; 10 s
C. Moon; 18 s (Correct answer)
D. Moon; 20 s

Step 1

Step 1 — Bridge: maximum height (m) in Table 1 and x-axis of Figure 1.

Step 2

Step 2 — Table 1: highest height = Moon (122 m).

Step 3

Step 3 — Figure 1: Moon data point at x=122 → y=18 s.

Step 4

Step 4 — Answer: Moon; 18 s. Option C.

Correct answer: C

Why C is correct

Moon = highest height (122m) → 18s flight time. Correct.

Why other options are wrong

A: Earth = lowest height and shortest flight. Incorrect.

B: Mars = second-highest, not the longest. Incorrect.

D: 20 s is the top of the y-axis scale, not the Moon's data point. Students misread 18 as 20. Incorrect.

⚠ Trap: Option D exploits axis-scale confusion: y-axis goes to 20s and students glance at the scale top instead of reading the Moon data point's y-position at 18s.

Strategy Tips

Preview all figure titles before reading questions — 20 seconds to know where to look
Underline the bridge variable name in both figure labels
Write the intermediate value physically before going to the second figure
Describe each figure's trend in one adjective before comparing
If stuck, check whether trial numbers in a table match x-axis labels in a nearby graph

Common pitfalls

Using only one figure when two are needed

Carrying the wrong intermediate value — re-verify before Step B

Assuming figures show the same trend without checking axis directions

Multi-figure questions legitimately take 60–90 seconds. Budget accordingly — do not rush the second lookup.

Summary

Every multi-figure question has a bridge variable — find it first, then execute a two-step transfer
Write your intermediate value before looking at the second figure
Trend comparison: describe each figure in one word before comparing

Take any two related data tables. Practice identifying a shared variable (the bridge), extracting a value from the first, and looking it up in the second. Repeat with three different pairs.

Next: Experimental Design: Variables and Controls All ACT Science lessons