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Last Updated on May 4, 2023
GMAT OFFICIAL GUIDE PS
Solution:
For this overlapping sets problem we can use the following equation:
Total percent = % in category A + % in category B – % in both categories + % in neither categories
Since the answer choices are in percentage form we can use 100 as the total. We are given that 75 percent of a class answered the first question on a certain test correctly, 55 percent answered the second question on the test correctly, and 20 percent answered neither of the questions correctly. Using these values, we have:
100 = 75 + 55 – B + 20
100 = 150 – B
B = 50
Answer: D
