Official Guide Explanation:
Problem Solving #61

Background

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Solution and Metadata

Question: 61
Page: 160
Difficulty: 5 (Moderate)
Category 1: Arithmetic > Ratio and Proportion >
Category 2: Word Problems > Mixture Problems >

Explanation: This question boils down to a simple ratio. If a glucose solution consists of 15 grams of glucose per 100, we can write that as a fraction: (15/100). However, we're interested in how much glucose is in 45 cubic centimeters of the solution: ((x)/45). Since the ratio of glucose to total solution will always be the same, we can set the fractions equal to each other: (15/100) = ((x)/45). Simplify by multiplying both sides by 45: ((15(45))/100) = x. Instead of multiplying 15 and 45, look for factors that can cancel: ((5(3)(5)(9))/(5(5)(4))) = (27/4) = 6(3/4) = 6.75, choice (E).

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