A certain protective additive increases from 20 days to 25 days the time between required maintenance checks on an industrial vehicle. By what percent is the time between maintenance checks increased by using the additive?  Choose the correct choice from the following answers
A) 25 %
B) 33 1 / 3 %
C) 50 %
D) 66 2 / 3 %
E) 75 %

Rationale: "general formula for percent increase or decrease , ( percent change ) : percent = change / original ∗ 100 so , the time between maintenance checks increased by 25 − 20 / 20 ∗ 100 = 25 answer : a ."
Answer: A