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1. A and B can do a work in 12days,B and C in 15days,C and A in 20days.If A,B and C work together ,They will complete the work in:

  • A. 5days
  • B. 5days
  • C. 5days
  • D. 5days

Answer: Option C

Explanation:

A + B can do the work in 12 days.

In a single day A + B will do 1/12 th portion of the work.

B + C can do the work in 15 days.

In a single day B + C will do 1/15 th portion of the work.

A + C can do the work in 20 days.

In a single day A + C will do 1/20 th portion of the work.

In a day (A + B) + (A + C) + (C + A) will do = (1/12) + (1/15) + (1/20) portion of the work.

2(A + B + C) = (1/12) + (1/15) + (1/20) = 1/5 portion of the work.

Then, (A + B + C) will do = 1/10 portion of the work in a day

A + B + C will complete the work in 10 days.


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