Last Updated on May 4, 2023
GMAT OFFICIAL GUIDE PS
Solution:
Let’s first determine the average of 10, 30, and 50, using the average formula.
average = sum/quantity
average = (10+30+50)/3
average = 90/3
average = 30
We can now rephrase the question to ask: “30 is 5 more than the average of 20, 40, and what value?” Let’s label the missing value as n and create an equation.
30 = (20+40+n)/3 + 5
25 = (20+40+n)/3
75 = 60 + n
15 = n
Answer: A