Question

A can do a piece of work in 25 days. While B alone can do in 20 days. A started the work and was Joined by B after 10 days. The work lasted for
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Answer 1

A can do a piece of work in 25 day

so 1 day - 1 by 25

b can do a piece of work in 20 days

so 1 day- 1 by 20

the work lasted - 1 by 25 added 1 by 20 - 7 by 60

so work lasted in 60 by 7