Single correct option
A's monthly salary is 25% more than B's. C's monthly salary is 20% less than A's. Which of the following is true?
- A. C earns 5% more than B
- B. C and B earn the same amount
- C. C earns 5% less than B
- D. C earns 4% less than B
Show answer and solution
Answer: (B) C and B earn the same amount
Take B = 100. Then A = 125 (25% more). C is 20% less than A, so C = 125 × 0.8 = 100. Hence C = B.
Why the traps fail: adding and subtracting percentages (+25 − 20 = +5) is wrong because the 20% is computed on a larger base (A), not on B.
Tip: a 25% rise is undone by a 20% fall, since 1.25 × 0.8 = 1. In general, a rise of 1/n is cancelled by a fall of 1/(n+1).
Why the traps fail: adding and subtracting percentages (+25 − 20 = +5) is wrong because the 20% is computed on a larger base (A), not on B.
Tip: a 25% rise is undone by a 20% fall, since 1.25 × 0.8 = 1. In general, a rise of 1/n is cancelled by a fall of 1/(n+1).
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