Multiple choice

A, B and C can complete a work in 20 days working together. A and B together are 50% more efficient than C and A & C together are 100% more efficient than B. Then in how many days A alone can complete the work?

  1. 85 days

  2. 80 days

  3. 75 days

  4. 65 days

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

Let efficiencies be A, B, C. (A+B+C) = 1/20. (A+B) = 1.5C. (A+C) = 2B. Solving the system: A+B+C = 1.5C + C = 2.5C = 1/20 => C = 1/50. A+C = 2B => A+1/50 = 2B. A+B+1/50 = 1/20 => A+B = 3/100. Solving gives A = 1/75. A takes 75 days.

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