Official Guide Explanation:
Problem Solving #169




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Solution and Metadata

Question: 169
Page: 176
Difficulty: 5 (Moderate)
Category 1: Word Problems > Rate Problems > other
Category 2: Arithmetic > Ratio and Proportion >

Explanation: This is a simple ratio question made more difficult with very large numbers. It's handy to know that 1 million = 1 * 106, and the question tells you that 1 billion = 1,000,000,000 = 1 * 109. Scientific notation will make this question a lot more straightforward. Set up the ratio like this:

(96/(100 * 106)) = ((x)/(3 * 109)). Convert 100 * 106 to 1 * 108, then cross - multiply:

96 * 3 * 109 = x * 108 Divide both sides by 108:

x = 96 * 3 * 10 = 288 * 10 = 2,880, choice (C).

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