Multiple choice

A and B can do a work in 12 and 15 days respectively. Together they can do it in?

  1. 20/3 days

  2. 6.5 days

  3. 6.6 days

  4. 7 days
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The combined work rate is 1/12 + 1/15 = 5/60 + 4/60 = 9/60 = 3/20. The time taken to complete the work together is the reciprocal of the combined rate, which is 20/3 days.

AI explanation

Using the combined work formula, their one day work is the sum of their individual rates, which is 1/12 plus 1/15. Finding a common denominator of 60, this sum becomes 5/60 plus 4/60, which equals 9/60 or 3/20. The total time to complete the work is the reciprocal of their combined daily rate, so the time is 20/3 days.

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