Multiple choice

A alone can complete a job in 20 days while B alone can complete it in 25 days. In how many days will the job be completed if they work on alternate days?

  1. 13.33 days

  2. 13 days

  3. 13.5 days

  4. cannot be determined
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The problem states they work on alternate days, but does not specify who starts first. Since the order of starting (A then B vs B then A) changes the total time taken, the answer cannot be determined.

AI explanation

A complete the job in 20 days and B in 25 days, but the starting person is not mentioned. Because we don't know whether A or B works on the first day, the total duration cannot be calculated accurately. The result is that it cannot be determined.

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