Official Guide Explanation:
Problem Solving #58




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Solution and Metadata

Question: 58
Page: 69
Difficulty: 4 (Moderately Easy)
Category 1: Arithmetic > Fractions >
Category 2: Arithmetic > Decimals >

Explanation: This is solvable via long division, but there's almost always a better way. Note that the numerator and denominator aren't that much different from 30 and 120, so the fraction is probably about (1/4). (If you only get that far, you can narrow the choices down to (A) and (B), a pretty good start.) However, you can do better. The equivalent of (1/4) with 31 in the numerator is (1/4)((31/31)) = (31/124). (31/125) has a slightly larger denominator, so it is equal to a slightly smaller number. The only answer choice that is slightly smaller than (1/4) is 0.248, choice (A).

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