Multiple choice

A B and C can do a piece of work in 50, 75 and 20 days respectively. They all work together for 4 days, then C left the work.Then find out in how many days A and B take to finish the rest of the work?

  1. 20

  2. 30

  3. 18

  4. 24
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In 4 days, A does 4/50, B does 4/75, C does 4/20 = 1/5. Total done = 4/50 + 4/75 + 4/20 = 12/150 + 8/150 + 30/150 = 50/150 = 1/3. Work remaining = 2/3. A+B's combined rate = 1/50 + 1/75 = 5/150 = 1/30. Time needed = (2/3) / (1/30) = 20 days.

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