Multiple choice

A alone can do a piece of work in 6 days and B alone can do it in 8 days. A and B undertake it for Rs. 640. With the help of C, they finish it in 3 days. How much will C be paid?

  1. Rs. 60

  2. Rs. 80

  3. Rs. 100

  4. Rs. 120
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A's rate = 1/6, B's rate = 1/8. Together with C, they finish in 3 days, so A+B+C = 1/3. C's rate = 1/3 - (1/6 + 1/8) = 1/3 - 7/24 = 1/24. C's share = (1/24) / (1/3) * 640 = (1/8) * 640 = 80.

AI explanation

Using the LCM method, let the total work be 24 units. The efficiencies of A and B are 4 and 3 units per day respectively, while their combined efficiency with C is 8 units per day. This means the efficiency of C is 8 minus 7, which is 1 unit per day. Since the total wages are proportional to efficiency, C gets 1 divided by 8 of the total Rs. 640, which equals Rs. 80.

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