2016 AMC 8 Problems/Problem 3

3. Four students take an exam. Three of their scores are $70, 80,$ and $90$ . If the average of their four scores is $70$ , then what is the remaining score?

$\textbf{(A) }40\qquad\textbf{(B) }50\qquad\textbf{(C) }55\qquad\textbf{(D) }60\qquad \textbf{(E) }70$

Solution

We see that $80-70=10$ and $90-70=20$ . We then find that $10+20=30$ . We want our average to be $70$ , so we find $70-30=40$ . So our final answer is $\boxed{\textbf{(A) }40}$

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2016 AMC 8 Problems/Problem 3

Solution