Most Important Concepts for the ACT

Our partners at Method Test Prep and Evan Wessler had a great list of the concepts you definitely need to review and practice with before test day. Here they are, by section.


  • Punctuation. There are so many punctuation-based questions on the ACT English that you could easily raise your section score just by studying your commas, semicolons, and apostrophes. Make sure you know your rules cold, and that you know how to apply them. The following is a great example of one way the ACT can trick you with improper punctuation. We’re used to seeing however and other similar transition words as asides that highlight a contrast. This, however, is not the only way these words can be used. (See what I did there?) Sometimes, they begin new sentences in contexts that resemble the “aside” scenarios. The ACT consistently tests whether you can tell the difference.

The project began on May 9, 1958, however,  residents had to wait ten more years for real progress.

The project began on May 9, 1958; however,  residents had to wait ten more years for real progress.

  • Subject-verb agreement. On each ACT, the number of subject-verb agreement questions are about the same; there are lots of them. Know how to recognize questions that test this concept, and how to break a sentence down to recognize the subject that is doing the verb. Speaking of which, did you notice the subject-verb error in the first sentence of this paragraph? The are should be an is. Why? The subject is number, not questions, and since number is a singular word, the sentence must employ a singular verb to agree with it. Techniques like recognizing prepositional phrases, whereby you can simplify the sentence by crossing out pieces that hide the subject, can come in handy. Here’s how that first sentence would read if we applied this technique.

On each ACT, the number of subject-verb agreement questions are about the same.

On each ACT, the number of subject-verb agreement questions is about the same.


  • Ratios and proportions. We at MTP have a saying we like to use: when all else fails on the ACT Math, use proportions. We’re only half-joking here: many word problems and geometry problems (similar triangles and scale models, for example) hinge entirely on setting up a correct proportion. Make sure you can recognize these scenarios and correctly set up both direct and indirect proportions.
  • Simple probability and counting problems. You go into a diner with a prix fixe menu from which you can order one of eight appetizers, one of twelve entrées, and one of five desserts. If you order one appetizer, one entrée, and one dessert at random, what is the probability of ordering any given prix fixe combination? Do you know? This question provides an example to a very common type of ACT math problem. Basic probability and counting principles show up early and often, so make sure you know how to handle them. Any by the way, the probability that you order any one combination is 1/480. Eat up!
  • Right triangle geometry & trigonometry. You are very likely to see right triangles and other related geometry/trigonometry on the ACT. Know your trig functions and how to use them to find sides and angles of triangles. Special right triangles show up consistently, as do some intermediate trigonometry concepts. If you haven’t yet taken trigonometry, learn the basic trigonometric functions and SOH-CAH-TOA. You’ll be happy you did.


  • Finding information using key words. Every ACT Reading section has questions that ask you for a specific detail. Unfortunately, you are often expected to find this information without any line references. This sounds bad, but it doesn’t need to be. In almost all questions of this type, you can distinguish and look for key words that are likely to show up in the text verbatim. For example, consider the question below.

The passage makes clear that the gestation period of the quokka is similar to that of a:

A. house mouse.
B. rabbit.
C. muskrat
D. opossum.

The “key” word is something that is likely to be particular to the question, and is unlikely to be found frequently throughout the passage. Here, that word is gestation. On top of that, you can look for any of the names of the four animals listed in the choices, which are also likely to appear only once in the passage. In this way, you can efficiently find information without wasting time.

  • Discerning the main idea. About 80 percent of the questions on the ACT test the main idea or purpose of an individual word, a phrase, a paragraph, or the passage as a whole. This means you need to avoid making assumptions and must focus on the overall point the author is trying to make. This is so even with more figurative language. Take, for example, this excerpt and question.

In their efforts to determine the biodynamic rhythms of an ecosystem, environmentalists can end up mistaking the forest for the trees. By focusing on individual species and their isolated processes, they run the risk of ignoring broader interspecies interactions, especially those that exist between plants and animals.

In asserting that environmentalists “mistake the forest for the trees, ” the author most nearly means that environmentalists often:

A. assume that entire forests consist of a single species of tree.
B. forget entirely to consider how ecosystems work.
C. possess a view of ecosystems that is too narrow.
D. consider interactions between plants and animals to be less worthy of study.

If you’re not careful, you can fail to consider the broader idea of a paragraph, and instead focus on individual details to guide your answers. This is a mistake, because main idea questions almost always gauge your skills in seeing the big picture. Without looking at the choices, and even without fully understanding the idiomatic phrase highlighted by the question, we can discern that the excerpt is focused on how environmentalists may focus on individuals and separate processes rather than on larger interactions: these scientists, according to the author, pay attention to the small instead of the large context. The answer that encapsulates this best is choice C. Notice, though, how the other choices all try to fool you by bringing up specific words, terms, or ideas that are in the excerpt. To avoid getting fooled, zoom out and consider the larger idea!


  • Data interpretation. Our most experienced tutors all agree: more than half the incorrect ACT Science answers we see students provide are due to mistakes in obtaining or reading information in the passage. Take this graph and question, for example.

According to the figure, by 8 hours after incubation with the antibiotic, the percentage of bacteria that had been eliminated was approximately:

A. 20%
B. 40%
C. 60%
D. 80%

If you picked choice A, you were fooled. Many students do not look at the axes before they answer questions, and it costs them dearly. Notice how the vertical axis is measuring percent bacterial survival, whereas the question is asking for the percent of bacteria eliminated. By the eighth hour, just under 20% of bacteria had survived, meaning just over 80% had been eliminated. Lesson learned: when you go looking for data,  read your axes,  make sure you’re looking the right place, and never simply assume a table or graph is showing what you think it’s showing.

  • Text-based information. There are certain questions on the ACT Science that require you to extract information not from figures or tables, but from text. Practice full-length Science sections, taking special note of questions that ask about a procedure or detail of the experiment. They’re more common than you think. When in doubt, consult the text for essential information: you’ll likely find it.
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