Multiple choice

A can do a piece of work in 21 days. B is 40% more efficient than A. The number of days required for B to finish the same work alone will be

  1. 10

  2. 12

  3. 15

  4. 18
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A takes 21 days. B is 40% more efficient, meaning B's efficiency is 1.4 times A's. Time taken by B = 21 / 1.4 = 210 / 14 = 15 days.

AI explanation

The formula for time taken by a more efficient worker is Base Time x (Base Efficiency / New Efficiency). A takes 21 days and B is 40% more efficient, making the efficiency ratio 1:1.4 or 5:7. Therefore, B requires 21 x (5/7) = 15 days to finish the work.

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