Multiple choice

A and B together can do a piece of work in 20 days and A alone can do it in 30 days. B alone can do the work in how many days?

  1. 45

  2. 60

  3. 54

  4. 30
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Use work rates: A+B together complete 1/20 of work per day. A alone does 1/30 per day. So B's rate = 1/20 - 1/30 = 3/60 - 2/60 = 1/60 per day. Therefore B alone needs 60 days. Option A (45) and C (54) are common errors from incorrect arithmetic, while D (30) is A's time.

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