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Tip #29 to Get a Top ACT Math Score (page 2)

By McGraw-Hill Professional
Updated on Sep 7, 2011

1. C Great springboard question. When you see a question like this, ask yourself, "Self, how do these equations relate?" There must be a quick easy way to do this, that's how they design the ACT. That's where springboard comes in. It tells you to factor whenever you can–if you can factor, that's what they want you to do, it's how to get the question correct. When you factor the second equation, you get
2. z = 6(xy) – 5. Since we know that

xy = 4, we plug in 4 for the xy to get

z = 6(4) – 5 = 19. Nice!

Moral of the question: Always ask, "How do the two equations relate?"

3. F The ACT loves x2 – 49. When you see x2 – 49, factor it to (x – 7)(x + 7). Then the next step becomes clear–springboard helps you see what to do next. You don't even need to see it all in advance, just take it one springboard step at a time. So once you write (x – 7)(x + 7), you see that there is an (x – 7) on top too. Rewrite (x – 7)2 as (x – 7)(x – 7), and reduce/eliminate one of the (x – 7)'s:
4. C Nine out of ten kids freak out, guess, and move on. But if you translate fractions to decimals, it's so easy! I love this strategy! So
5. Then, just convert the answer choices and choose the best fit. Choice C is correct because

6. F Springboard, baby! Springboard helps you see what to do next. Follow all our springboard rules: When you have two equations like this, ask, "How are they connected; what's the back door?" Just asking the question usually helps you find the connection. Then you notice that means that a = 8b. (When you see a proportion, cross-multiply. It's how the ACT works! It's always the way to get the answer.) Next springboard rule: "When you see x2y2, factor it to (xy)(x + y)." Guaranteed, if you see a2 – 64b2, that's what you need to do. So a2 – 64b2 = (a – 8b)(a + 8b). Lastly, plug 8b in for a to get (8b – 8b)(8b + 8b) = 0, since 8b – 8b = 0. Nice. Now that was fun.

Go to: Tip #30