ACT^® Practice Test

ACT practice questions with answers and explanations:

1. Which of the following would be the best replacement for the highlighted portion of the sentence below?
   While all dogs descend through gray wolves, it’s easy to notice that dog breeds come in a variety of shapes and sizes.
   • No change
   • descend by gray wolves
   • descend from gray wolves — Correct answer
   • descended through gray wolves
   Explanation: The correct preposition here is from. The point of origin for dogs is gray wolves. Through implies a point of origin beyond gray wolves, and by implies the gray wolves are personally responsible for their descendants.
2. Kael is visiting another state that has a different sales tax rate than his home state. He has purchased some items that total $87.53, and his total bill came to $94.26. What was the sales tax rate on his purchase?
   • 5.89%
   • 6.21%
   • 6.95%
   • 7.69% — Correct answer
   Explanation: To calculate the sales tax amount, subtract the cost of the items from the total bill:

   \($94.26-$87.53=$6.73\)

   Then, divide the tax amount by the pretax purchase amount:

   \($6.73 \div $87.53=0.0769\)

   To convert a decimal to a percentage, multiply by 100. To do this, simply move the decimal two places to the right to get 7.69.
3. If \(f(x)=4x+2\), and \(f^{-1}(x)\) is the inverse function for \(f\), then what is \(f^{-1}(6)\)?
   • \(\frac{1}{2}\)
   • 1 — Correct answer
   • \(\frac{3}{2}\)
   • 2
   Explanation: If \(y=f^{-1}(6)\), then \(y\) must satisfy \(f(y)=6\). Substituting and solving for \(y\) yields \(4y+2=6\), then \(4y=4\), and \(y=1\).
4. What is the definition of the word haunt in the following passage?
   From that time forward, Mr. Utterson began to haunt the door in the by-street of shops. In the morning before office hours, at noon when business was plenty and time scarce, at night under the face of the full city Moon, by all lights and at all hours of solitude or concourse, the lawyer was to be found on his chosen post.
   • To levitate
   • To constantly visit — Correct answer
   • To terrorize
   • To daunt
   Explanation: The mention of morning, noon, and night make it clear that the word haunt refers to frequent appearances at various times. The word does not mean to levitate, terrify, or mock someone in this context.
5. Based on the data below, what was the lowest nitrate concentration at which the average growth rate of Species A was at least 0.5 division per day greater than that of Species B?
   Scientists investigated how nitrate concentration affects the growth of two freshwater algal species. They prepared culture containers containing nitrate concentrations of 0, 2, 4, 6, or 8 mg/L. Each container received teh same amount of algae and was maintained under identical light, temperature, and water conditions.
   
   After 10 days, the scientists calculated the average growth rate of each species in divisions per day. Each point in Figure 1 represents the mean growth rate from five cultures.
   
   
   • 2 mg/L
   • 4 mg/L
   • 6 mg/L — Correct answer
   • 8 mg/L
   Explanation: At 4 mg/L, Species A grew at approximately 1.6 divisions per day, while Species B grew at approximately 1.2 divisions per day. The difference was only 0.4 divisions per day.
   
   At 6 mg/L, Species A grew at approximately 1.9 divisions per day, while Species B grew at approximately 1.3 divisions per day. The difference was approximately 0.6 divisions per day. Therefore, 6 mg/L was the lowest concentration that met the condition.