Answer: 17%
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Step-by-step explanation:
The change in value is 30-25 = 5, so the amount has dropped by 5
Divide this change over the original amount to get 5/30 = 0.1667 approximately. This converts to 16.67% roughly, and that rounds to 17%
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Here's a way to do it using a formula
A = old value = 30
B = new value = 25
C = percent change
C = [ (B-A)/A ] * 100%
C = [ (25-30)/30 ] * 100%
C = -0.1667 * 100%
C = -16.67%
C = -17%
The negative percent change means we have a percent decrease. The class size went down by about 17%.