Multiple choice

A does 80% of a work in 20 days. Then, B joins him and they together finish the remaining work in 3 days. How long would B alone take to do the whole work?

  1. 75 days

  2. 37.5 days

  3. 17.5 days

  4. 35 days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A does 80% in 20 days, so A does 4% per day. Remaining work is 20%. A and B do 20% in 3 days, so they do 20/3 % per day. B's rate = (20/3) - 4 = 8/3 % per day. B takes 100 / (8/3) = 300/8 = 37.5 days.

AI explanation

If A completes 80% of the work in 20 days, A's total time to complete the whole work alone is 20 / 0.8 = 25 days, meaning A does 4% of the work daily. The remaining work is 20%, which A and B finish in 3 days, meaning their combined daily progress is 20/3 %. The daily work of B alone is 20/3 % - 4 %, which equals 8/3 %. Therefore, B alone would take 100 / (8/3) = 300/8 = 37.5 days to complete the entire work.

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