Multiple choice

To do a certain work, the ratio of efficiencies of A and B is 3 : 7. Working together, they can complete a work in 14 days. B started the work and after working for 8 days, he left and A completed the remaining work. For how many days did A work?

  1. 28

  2. 30

  3. 24

  4. 27
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let efficiencies be 3x and 7x. Total work = (3x + 7x) * 14 = 140x. B works for 8 days, completing 7x * 8 = 56x. Remaining work is 140x - 56x = 84x. A completes this at 3x efficiency, taking 84x / 3x = 28 days.

AI explanation

Let the efficiencies of A and B be 3 units and 7 units per day respectively. Their combined efficiency is 10 units per day, meaning the total work is 10 units multiplied by 14 days, which is 140 units. When B works alone for 8 days, the work completed is 7 units per day multiplied by 8 days, giving 56 units. The remaining work is 140 minus 56, which is 84 units. A completes this remaining work at 3 units per day, so A works for 84 divided by 3 days, which equals 28 days.

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