Multiple choice

A and B can do a piece of work in 72 days. B and C can do it in 120 days. C and A can do it in 90 days. In how many days all three together can do the work?

  1. 80 days

  2. 120 days

  3. 100 days

  4. 60 days

  5. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When we add the work rates of all three pairs (A+B, B+C, C+A), we get 2(A+B+C) = 1/72 + 1/120 + 1/90 = 12/360 = 1/30. Therefore A+B+C's combined rate is 1/60 work per day, meaning they complete the work in 60 days.

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