Education.com
Try
Brainzy
Try
Plus

# Tip #18 to Get a Top ACT Math Score (page 3)

By McGraw-Hill Professional
Updated on Sep 7, 2011

1. B This question intimidates some students; it seems too theoretical. But "Make It Real" makes it so easy. Just choose a real number for p (remember that the question says that the number that you choose has to be odd). Let's say p = 5. Then try p = 5 in all the answer choices to see which one does what the question asks, which one gives an odd number. The answer is B since 2(5) – 1 = 9.
2. J First, "product" means "multiply." We will review this more in Skill 27. "Make It Real," let's say, m = –3 and n = 3. Now it's easy, the product (multiplication) of –3 and 3 is –9. Choice J looks good, but to be safe, try a few more possibilities. After you've done three, you can be sure that your answer is correct. And by then you might realize that "Of course, a positive times a negative is always a negative."
3. D Choose a number for b, let's say b = 5 (notice the question states that b can be any real number besides 3 and 7). Now it's easy, solve:
4. Skill 12 review: the value of b cannot equal 3 or 7 because either number would give us a 0 on the bottom of the fraction, which is illegal in math and would cause the equation to be "undefined" and would cause lots of important folks to get very upset.

5. H We are into the "hards" now. But "Make It Real" will knock these down a notch to mediums or even easies. Let's say k = 100 and q = 20. So, of the 100 kids in a class, 20 have NOT seen Monty Python and the Holy Grail. Once we've "Made It Real," it becomes obvious that if 20 have NOT seen it, then 80 have seen it. (When you are using "Make It Real" with percents, use 100 when you can, it makes questions really easy.) Now, based on k = 100 and q = 20, we want an answer of 80. So try each answer choice, using k = 100 and q = 20 and find the one answer choice that equals 80.
6. Choice H is correct because

If two choices work, just choose new "Make It Real" numbers and have a tiebreaker.

People think that this might take forever to do, but try it; it takes like 30 seconds.

7. E Let's say m = 3 and n = 5. Then –3m – 2n – 4 = –3(3) – 2(5) – 4 = –23. The question asks what happens when m increases by 2 and n decreases by 1, so let's solve for m = 5 and n = 4. Now, –3m – 2n – 4 = –3(5) – 2(4) – 4 = –27. So the result changed from –23 to –27; it decreased by 4.

Go to: Tip #19