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Two Types of Tricky ACT Science Questions

Most ACT Science passages end with a pair of especially challenging questions. One of these questions will be legitimately difficult to solve. The other question, however, will be designed to appear much tougher than it actually is. These “trick questions” usually follow one of two patterns: drawing on data from the passage that none of the other questions require or trying to get students to make erroneous assumptions about the design of the experiment.


Type 1: Unused Data

“Unused data” questions require you to identify a piece of information from the passage that has not been needed to answer any of the previous questions. Often this data will be something small, such as a unit of measure used in the passage. Indeed, that is precisely what is happening in the following question from Practice Test 1 in The Official ACT Prep Guide, 2018 Edition:


  1. Which of the scientists, if any, would be likely to agree that the Sun could have    formed entirely by accretion?


  1. Scientist 1 only
  2. Scientist 3 only
  3. Scientists 1, 2, and 3
  4. None of the scientists


In the passage that accompanies this question, three scientists are arguing over the maximum mass that a star can achieve by various processes, including accretion (gradual accumulation). Scientist 1 says that the maximum by accretion is 15 MS, scientist 2 says that the maximum is 30 MS, and scientist 3 says that there is effectively no maximum.


The key to answering this question successfully is to recognize what the scientistS are using to measure the mass of stars in the first place. If you read through the passage, you’ll see this snippet information buried in parentheses:


1 MS = mass of the Sun


The unit of measure in this passage is solar mass, or the mass of our own Sun. All three scientists would agree that the Sun could have been formed entirely by accretion because there maximums are 15 times the mass of the Sun, 30 times, and no limit, respectively. Therefore, choice J is the correct answer.


Type 2: Faulty Assumptions

A “faulty assumption” question tries to get you to make a reasonable but false assumption about the design of an experiment. For this type of question, we’re going to use a simplified example that focuses on where the faulty assumption comes into play.


In our example, students are conducting three experiments. In the first experiment, the students use a 100 ml beaker. In the second experiment, the students use the same beaker but change some of the other variables. (Exactly what these variables are is irrelevant for our purposes.) The third experiment shows the students running a more comprehensive series of tests:


The students collected multiple beakers, each of a different capacity.

Capacity (ml)


Now that we have all of the information we’ll need, let’s look at the “faulty assumption” question:


What is the minimum number of beakers require to conduct all three experiments?

  1. 7
  2. 5
  3. 4
  4. 3


It’s easy to eliminate C and D because experiment 3 alone uses 5 beakers. Now things get a bit more difficult. We know the minimum number can’t be 7 (choice A) because experiments 1 and 2 use the same beaker. But how can it be 5 (choice B)? The trick here is to look at the capacities of the beakers being used for experiment 3. If we look carefully, we can see that one of the beakers has a 100 ml capacity, the same capacity as the beaker used for experiments 1 and 2. In other words, the student could have reused the beaker from the first two experiments for the final one.


The ACT doesn’t want you to do this. Instead, the test designers are hoping that you’ll assume (erroneously) that the students need five entirely new beakers for experiment 2. However, there is no reason that they couldn’t have just washed out the old 100 ml beaker and used it again.