AMC8 2010 Problem 9

Ryan got 80 \% of the problems correct on a 25 -problem test, 90 \% on a 40 -problem test, and 70 \% on a 10-problem test. What percent of all the problems did Ryan answer correctly?

Answer Choices
A. 63
B. 75
C. 80
D. 84
E. 86