# Difference between revisions of "2001 AMC 12 Problems/Problem 4"

## Problem

The mean of three numbers is $10$ more than the least of the numbers and $15$ less than the greatest. The median of the three numbers is $5$. What is their sum?

$\text{(A)}\ 5\qquad \text{(B)}\ 20\qquad \text{(C)}\ 25\qquad \text{(D)}\ 30\qquad \text{(E)}\ 36$

## Solution

Let $m$ be the mean of the three numbers. Then the least of the numbers is $m − 10$ (Error compiling LaTeX. ! Package inputenc Error: Unicode character − (U+2212)) and the greatest is $m + 15$. The middle of the three numbers is the median, 5. So $\dfrac{1}{3}[(m-10) + 5 + (m + 15)] = m$, which implies that $m=10$. Hence, the sum of the three numbers is $3(10) = 30$, and the answer is $\text{(D)}$.