WBCS.LIVE practice question

A certain work can be done by A and B in 6 days, by B and C in 12 days. If C, alone can do the same work in 36 days then how long will it take to finish the work by working A, B and C together?

Solve this multiple-choice question and check the correct answer with its explanation below.

Answer options

  1. 5\frac{1}{7} days
  2. 5\frac{2}{7} days
  3. 5\frac{3}{7} days
  4. 5\frac{4}{7} days

Correct answer and explanation

Correct answer: 5\frac{1}{7} days

Explanation: āœ… Correct Answer: A. 5\frac{1}{7} days šŸ“š Explanation: A and B's rate is 1/6, B and C's is 1/12, and C's is 1/36. This means B's rate is (1/12 - 1/36) = 2/36 = 1/18. Then A's rate is (1/6 - 1/18) = 2/18 = 1/9. The combined rate of A, B, and C is (1/9 + 1/18 + 1/36) = 7/36. The time to finish is the reciprocal 36/7, which equals 5 and 1/7 days.