5. On a test consisting of 60 questions, Susan answered 90 percent of the first 50 questions
correctly. What percent of the other 10
questions does she need to answer correctly for
her grade on the entire exam to be exactly
80 percent?
(A) 30 percent
(B) 40 percent
(C) 50 percent
(D) 60 percent

A) 30 percent

Explanation: For Susan’s grade to be exactly 80 percent, she must answer .8(60) = 48 questions correctly. If she answered 90 percent of the first 50 questions correctly, then she answered .9(50) = 45 questions correctly so far, which means she must answer 3 of the remaining 10 questions correct for a grade of 80 percent. 3/10 = .3, which equals 30 percent.