Multiple choice

A can complete a piece of work in 30 days and B can do the same in 60 days. C is 50% more efficient than A. Find the number of days in which the work will be completed if A, B and C work together.

  1. 8 days

  2. 10 days

  3. 12 days

  4. 15 days

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

A = 1/30 work/day. B = 1/60 work/day. C is 50% more efficient than A, so C = 1.5 * (1/30) = 1/20 work/day. Combined rate = 1/30 + 1/60 + 1/20 = (2+1+3)/60 = 6/60 = 1/10. Time = 10 days.

AI explanation

Assume the total work is 60 units, making the efficiencies of A and B equal to 2 and 1 units per day respectively. Since C is 50 percent more efficient than A, the efficiency of C is 3 units per day. Working together, A, B and C have a combined efficiency of 6 units per day. Therefore, they complete the 60 units of work in 60 divided by 6 days, which equals 10 days.

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