2020 AMC 10A Problem 2

Below is the video solution and professionally curated solution for Problem 2 of the 2020 AMC 10A, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2020 AMC 10A solutions, or check the answer key.

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Concepts:mean

Difficulty rating: 560

The numbers $3, 5, 7, a,$ and $b$ have an average (arithmetic mean) of $15.$ What is the average of $a$ and $b?$

$0$

$15$

$30$

$45$

$60$

Video solution:

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Written solution:

The five numbers have total sum $5\cdot15=75$ . Since $3+5+7=15$ , we have $a+b=75-15=60$ , so the average of $a$ and $b$ is $30$ . Thus, C is the correct answer.

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