2016 AMC 8

Complete problem set with solutions and individual problem pages

Problem 3 Easy

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?

  • A.

    40

  • B.

    50

  • C.

    55

  • D.

    60

  • E.

    70

Answer:A

Let r be the remaining student's score. We know that the average, 70, is equal to \frac{70 + 80 + 90 + r}{4}. We can use basic algebra to solve for r:

\frac{70 + 80 + 90 + r}{4} = 70

\frac{240 + r}{4} = 70

240 + r = 280

r = 40

giving us the answer of \boxed{\textbf{(A)}\ 40}.