The given question is a GMAT 505 level problem solving percentage question. The concept tested in this GMAT sample question is finding out % increase and % decrease from a base value.

Question 8: 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?

- 60
- 80
- 40
- 120
- 160

@ INR

These are classic word problems. What is tested is one's ability to translate what is given in words into mathematical equations and expressions. Invest adequate time to understand what is stated and write correct equations. Usually, solving these equations will not be an issue.

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 difference between the value of x increased by 12.5% (i.e., A) and the value of x decreased by 25% (i.e., B) is 30.

i.e., 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 = \\frac{30}{37.5}) × 100 = 80

**The original number is 80**

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