Official Guide Explanation:
Problem Solving #101

Background

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Solution and Metadata

Question: 101
Page: 74
Difficulty: 5 (Moderate)
Category 1: Arithmetic > Percents > other
Category 2: Word Problems > Discount >

Explanation: To make things simple, adjust the numbers in two ways: convert them to scientific notation (that's much better than tracking all the zeroes) and approximate. So, since 1 billion = 10⁹, 115.19 billion can be written as 115 * 10⁹. 1 million = 10⁶ (that's something to memorize if you don't know it already), so 230.10 million can be written as 230 * 10⁶. We're interested in what percent of the profits were employee benefits, so we can set up a fraction:

((230 * 10⁶)/(115 * 10⁹)) = 2 * 10^{(6 - 9)} = 2 * 10^-3 = (2/(10³)) = (2/1000) = ((0.2)/100) = 0.2%, choice (E).

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