ACT Science Question and Answers 3 — Questions and Answers
Question 1: Experiment 1 tested four fertilizer types on corn yield. Fertilizer C produced the highest average yield at 8.4 tons/acre, while no-fertilizer control produced 4.1 tons/acre. What is the percent increase for Fertilizer C over the control?
- About 105% (Correct answer)
- About 51%
- About 200%
- About 75%
Correct answer: About 105%
Percent increase = (8.4 − 4.1)/4.1 × 100 = 4.3/4.1 × 100 ≈ 104.9%, approximately 105%.
Question 2: In a conflicting viewpoints passage, Student 1 argues that the universe is static and infinite, while Student 2 argues it is expanding from the Big Bang. The observed redshift of distant galaxies (light shifted toward longer wavelengths) best supports:
- Student 2, because redshift indicates galaxies are moving away (Correct answer)
- Student 1, because redshift proves the universe is stable
- Neither student, since redshift is unrelated to universe size
- Student 2 only if redshift is observed in nearby galaxies
Correct answer: Student 2, because redshift indicates galaxies are moving away
Redshift of distant galaxies indicates they are receding from us — consistent with an expanding universe, which supports Student 2's Big Bang hypothesis.
Question 3: A scientist studies how temperature affects cricket chirp rate. The data shows a linear increase in chirps per minute from 60°F to 90°F. At 60°F, the rate is 80 chirps/min; at 90°F, it is 200 chirps/min. What is the approximate chirp rate at 75°F?
- 140 chirps/min (Correct answer)
- 120 chirps/min
- 160 chirps/min
- 100 chirps/min
Correct answer: 140 chirps/min
75°F is halfway between 60°F and 90°F. Halfway between 80 and 200 is (80 + 200)/2 = 140 chirps/min.
Question 4: A study compares two antibiotics against Bacteria X. Antibiotic A creates a 25 mm zone of inhibition; Antibiotic B creates a 10 mm zone. What does this indicate?
- Antibiotic A is more effective against Bacteria X (Correct answer)
- Antibiotic B kills more bacteria per dose
- Both antibiotics are equally effective
- Antibiotic A is toxic to humans
Correct answer: Antibiotic A is more effective against Bacteria X
A larger zone of inhibition indicates greater effectiveness. Antibiotic A's 25 mm zone vs. Antibiotic B's 10 mm zone shows Antibiotic A is more effective against Bacteria X.
Question 5: Which of the following experimental designs best controls for the placebo effect in a drug trial?
- A double-blind placebo-controlled study (Correct answer)
- A study where all participants know they receive the drug
- An open-label study with a control group
- A study with no control group but careful observations
Correct answer: A double-blind placebo-controlled study
In a double-blind study, neither participants nor researchers know who receives the drug or placebo, eliminating bias from the placebo effect and researcher expectations.
Question 6: Table 1 shows that species diversity (number of species) in a forest decreased from 45 species to 12 species over 50 years of logging. Which additional data would best help determine whether logging caused the decline?
- Species diversity in similar unlogged forests over the same period (Correct answer)
- Rainfall data for the region over 50 years
- Soil nitrogen content before and after logging
- The financial value of the timber harvested
Correct answer: Species diversity in similar unlogged forests over the same period
Comparing species diversity in similar unlogged control forests would isolate whether logging (rather than climate or other factors) caused the decline.
ACT Science Question and Answers 3
Experiment 1 tested four fertilizer types on corn yield.
Fertilizer C produced the highest average yield at 8.4 tons/acre, while no-fertilizer control produced 4.1 tons/acre.
What is the percent increase for Fertilizer C over the control?