2019 AMC 12A Problem 2

Below is the professionally curated solution for Problem 2 of the 2019 AMC 12A, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2019 AMC 12A solutions, or check the answer key.

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Concepts:percentageratio and proportion

Difficulty rating: 770

2.

Suppose aa is 150%150\% of b.b. What percent of aa is 3b?3b?

5050

662366\dfrac{2}{3}

150150

200200

450450

Solution:

Since a=1.5b,a = 1.5b, we have 3ba=3b1.5b=2. \dfrac{3b}{a} = \dfrac{3b}{1.5b} = 2.

As a percentage, 3b3b is 200%200\% of a.a.

Thus, the correct answer is D.

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