Percents And Interest Problems

[swerve]

Enrollment in City College in 1980 was 83 1/3 percent of enrollment in 1990. What was the percent increase in the college’s enrollment from 1980 to 1990?

A. 10%
B. 16 2/3 %
C. 20%
D. 25%
E. 183 1/3%

The OA is C


Source: GMAT Prep

[Brent@GMATPrepNow]

Enrollment in City College in 1980 was 83 1/3 percent of enrollment in 1990. What was the percent increase in the college’s enrollment from 1980 to 1990?

A. 10%
B. 16 2/3 %
C. 20%
D. 25%
E. 183 1/3%

The OA is C


Source: GMAT Prep

A quick approach is to test values that satisfy the given information.

Given: Enrollment in City College in 1980 was 83 1/3 percent of enrollment in 1990
Important: We can save ourselves some time if we recognize that 83 1/3% is equivalent to 5/6.

So we can rewrite the given information as follows:
Given: Enrollment in City College in 1980 was 5/6 the enrollment in 1990

So, it COULD be the case that the 1990 enrolment was 6 students, and the 1980 enrolment was 5

What was the percent increase in the college’s enrollment from 1980 to 1990?
Percent change = (100)(new - old)/old
= (100)(6 - 5)/5
= (100)(1/5)
= 20%

Answer: C

Cheers,
Brent