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A driver increases his speed by 25%. By what percentage does the journey time decrease (for the same distance)?
A$25\%$
B$30\%$
C$15\%$
D$20\%$
Answer & Solution
Correct answer: D. $20\%$
Old speed → new speed = 1 → 1.25. Time scales inversely: new time = old time × 1/1.25 = old time × 0.80. Decrease = 1 − 0.80 = 20%.
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