2018 AMC 12B Problem 6

Below is the professionally curated solution for Problem 6 of the 2018 AMC 12B, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2018 AMC 12B solutions, or check the answer key.

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Concepts:ratio and proportionunit conversion

Difficulty rating: 1430

6.

Suppose SS cans of soda can be purchased from a vending machine for QQ quarters. Which of the following expressions describes the number of cans of soda that can be purchased for DD dollars, where 11 dollar is worth 44 quarters?

4DQS\dfrac{4DQ}{S}

4DSQ\dfrac{4DS}{Q}

4QDS\dfrac{4Q}{DS}

DQ4S\dfrac{DQ}{4S}

DS4Q\dfrac{DS}{4Q}

Solution:

One can costs QS\tfrac{Q}{S} quarters, which is Q4S\tfrac{Q}{4S} dollars. The number of cans that DD dollars can buy is

DQ4S=4DSQ. \dfrac{D}{\tfrac{Q}{4S}}=\dfrac{4DS}{Q}.

Thus, the correct answer is B.

Problem 6 in Other Years