The GMAT Sample Math question is an arithmetic problem solving question from the topic percentages and fraction. The concept tested is finding out % increase and % decrease from a base value.
The difference between the value of a number increased by 12.5% and the value of the original number decreased by 25% is 30. What is the original number?
A. 60
B. 80
C. 40
D. 120
E. 160
The correct choice is (B) and the correct answer is 80.
Let the original number be x.
Let A be the value obtained when x is increased by 12.5%.
Therefore, A = x + 12.5% of x
Let B be the value obtained when x is decreased by 25%.
Therefore, B = x - 25% of x
The question states that A - B = 30
i.e., x + 12.5% of x - (x - 25% of x) = 30
x + 12.5% of x - x + 25% of x = 30
37.5% of x = 30
x =
= 80
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