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# Tip #11 to Get a Top ACT Math Score (page 2)

By McGraw-Hill Professional
Updated on Sep 7, 2011

### Answers

Answer to Brian's Math Magic Trick #1—Multiples: You said carrot. How did I guess your vegetable? Check out my website for answers: www.BrianLeaf.com/carrot

1. D This question could be difficult, but "Use the Answers" makes it easy! Just test each answer choice by dividing it by 10, 12, and 15. The lowest choice that is divisible by 10, 12, and 15 is 60. Notice that several other answers work also, but 60 is the lowest. Make sure to try all choices.
2. G "Use the Answers."
1. 2 and 62—1cm = 62
2. 9 and 14—1cm = 126
3. 6 and 22—1cm = 66
1. 3 and 42—1cm = 42
2. 5 and 25—1cm = 25
3. D "Use the Answers" and it's easy! Just try each answer choice by dividing it by 60, 50, and 80. Choices A, B, and C don't even divide evenly by the three numbers—they are not multiples for all three. Choice D works, all three numbers divide evenly (without a decimal or fraction) into 1200. Choice E works also, but D is the lowest answer.
4. G "Use the Answers" and it's easy! Just try each answer choice by dividing it by 3, 4, 5, and 6, and then make sure there's an m and a p in there. Choice F doesn't divide evenly by 4. And choices H and K have more m's or p's than we need—we only need one of each. Choice J works, but G is the lowest answer. If that seems confusing, you can also "Make It Real" (Skill 18). Just choose easy numbers for m and p, such as 2 and 3, and then test the answers to find the least common multiple. Nice!
5. B This "superhard" question is easy for us. The hardest part for most kids is knowing what to do to solve it, i.e. recognizing it as a least common multiple question. But we know that every ACT has one, and we are watching for it, so we identify it and know what to do. Then just "Use the Answers," although you have to take the two peanuts off before you test each choice to see if it is the least common multiple. Choice B is correct since 362 – 2 = 360 which is the least common multiple of 8, 9, and 10.

Go to: Tip #12

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