Of the 720 students at a certain university, 25 percent are seniors.

Number of seniors= 720/4=180

\(\frac{180-x}{720-x}= \frac{1}{5}\)

900-5x=720-x
180=4x
x=45

Given:
1. Of the 720 students at a certain university, 25 percent are seniors.
2. x seniors were to graduate early and leave the university and no additional students entered or left the university

Asked: What value of x would reduce the number of seniors at the university to 20 percent?

1. Of the 720 students at a certain university, 25 percent are seniors.
Total students = 720
Seniors = 25% *720 = 180

2. x seniors were to graduate early and leave the university and no additional students entered or left the university

What value of x would reduce the number of seniors at the university to 20 percent?
Total students left = 720 - x
Seniors left = 180-x
Percentage of seniors = .2(720 - x) = 180 -x
144 - .2x = 180 - x
.8x = 36
x = 36/.8 = 360/8 = 45

IMO D

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