Multiple choice

A does 75% of a piece of work in 45 days. Then B joins him and they together finish the remaining work in 5 days. How long B alone would take to do the whole work?

  1. 15 days

  2. 45 days

  3. 60 days

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

A does 75% in 45 days, so 100% in 60 days. A's rate = 1/60 per day. Remaining work = 25%. A and B finish 25% in 5 days, so their combined rate = 0.25 / 5 = 1/20 per day. B's rate = (1/20) - (1/60) = 3/60 - 1/60 = 2/60 = 1/30. B takes 30 days.

AI explanation

A completes 75% of the work in 45 days, meaning A would complete the entire work in 60 days, making A's daily work rate 1/60. The remaining work is 25%, which A and B finish in 5 days, making their combined daily rate 1/20. By the work subtraction method, B's daily rate is 1/20 minus 1/60, equaling 2/60 or 1/30. Therefore, B alone would take 30 days to complete the whole work.

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