Multiple choice

E and F can do a piece of work in 10 days. If E alone can do it in 30 days, then F alone can do it in

  1. 15 days

  2. 20 days

  3. 25 days

  4. 18 days

  5. N/a
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If E and F together take 10 days, their combined rate is 1/10 per day. E's rate is 1/30 per day. F's rate is 1/10 - 1/30 = 2/30 = 1/15. Thus, F takes 15 days.

AI explanation

Let the total work be the least common multiple of the given days, which is 30 units. The combined efficiency of E and F is 30 units divided by 10 days, giving 3 units per day. E's individual efficiency is 30 units divided by 30 days, giving 1 unit per day. F's individual efficiency is 3 minus 1, yielding 2 units per day. Therefore, F alone will complete the 30 units of work in 15 days.

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