2001 AMC 10 Problem 16

Attempt Problem 16 of the 2001 AMC 10 below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2001 AMC 10 solutions, or check the answer key.

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16.

The mean of three numbers is 1010 more than the least of the numbers and 1515 less than the greatest. The median of the three numbers is 5.5. What is their sum?

55

2020

2525

3030

3636

Answer: D
Concepts:meanmedian (data)linear equation
Difficulty rating: 1280
Solution:

Let mm be the mean. The least number is m10m-10 and the greatest is m+15,m+15, with median 5.5.

Since the mean of the three is m,m, 13((m10)+5+(m+15))=m, \begin{aligned} &\tfrac13\big((m-10)+5+(m+15)\big) \\ &\quad =m, \end{aligned} which gives m=10.m=10.

The sum is 3m=30.3m=30. Thus, the correct answer is D.

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