Question

A, B and C together can do a piece of work in 12 days and A and B together can do the same work in 20 days. In how many days C working alone can finish the work?

Answer 1

Both A and B can complete 1/12th work in one day

So A+B=1/12 in one day

A alone can complete 1/20 th work

A=1/20 in one day

Now B alone how much work can complete

(1/20)+B=1/12

B =(1/12)-(1/20)

L.C.M of 12 and 20 is 60

So B=( (5–3)/60)

B=2/60=1/30

So alone can complete 1/30th work in one day

B alone can complete the work in 30 days

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