Official Guide Explanation:
Problem Solving #28

Background

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Solution and Metadata

Question: 28
Page: 65
Difficulty: 4 (Moderately Easy)
Category 1: Algebra > Equations >
Category 2: Word Problems > Rate Problems >

Explanation: This question is a straightforward one: it gives you an equation and the value of one variable to plug into it. After substituting in for the value for p, the equation looks like this: n = 300 - 20(10). To solve: n = 300 - 200 = 100. That's the number of calculators, so the revenue is (calculators)(price) = 100(10) = $1,000, choice (C).

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