Official Guide Explanation:
Problem Solving #D01

Background

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Solution and Metadata

Question: D01
Page: 20
Difficulty: 5 (Moderate)
Category 1: Arithmetic > Decimals >
Category 2: Algebra > Simplifying Algebraic Expressions >

Explanation: Judging from the answer choices, we shouldn't spend our time doing a lot of precise calculations. Start by figuring out how you would calculate the total amount spent by the customer. The first CD cost $15.95. A total of 6 discs were purchased, meaning there were 5 more than cost $3.99 each. We can express the total as:

15.95 + 5(3.99)

That doesn't directly match any of the choices. We can eliminate (B) and (E), since the 15.95 matches, but the other term does not. Also eliminate (C), since 5(4.00) is greater than 5(3.99), and 16.00 is greater than 15.95.

That leaves (A) and (D). (D) simplifies to 5(3.99) + 15.90. 5(3.99) matches our initial calculation, but 15.90 does not, so it must be incorrect. That leaves only (A).

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