2005 AMC 10B Problem 6

Problem 6 of 25EasierAlgebra

At the beginning of the school year, Lisa’s goal was to earn an A on at least

80\%

of her

50

quizzes for the year. She earned an A on

22

of the first

30

quizzes. If she is to achieve her goal, on at most how many of the remaining quizzes can she earn a grade lower than an A?

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Solution

Lisa needs an A on at least

0.8 \cdot 50 = 40

quizzes. She already has

22,

so she needs

40 - 22 = 18

A’s among the remaining

20

quizzes. That leaves at most

20 - 18 = 2

quizzes with a grade lower than an A. Thus, B is the correct answer.