Question

A,B,do a task in 12days,B,C do the same work in 15days,if C,A do the same task together in 20days,how many days A alone do that work??​

Answer 1

Answer:

A and B can do a piece of work in 12 days.

In 1 day, (A+B) can do 1/12th of the work.

B and C can do a piece of work in 15 days.

In 1 day, (B+C) can do 1/15th of the work.

A and C can do a piece of work in 20 days.

In 1 day, (A+C) can do 1/20th of the work.

Now, if we add on the work done by (A+B), (B+C) and (A+C), we will get the work done by (A+B+C) collectively in 1 day.

Therefore,

(A+B) + (B+C) + (A+C) = 1/12 + 1/15 + 1/20

2 (A+B+C) = 12/60

On simplification, we get

(A+B+C) = 1/10

It means that,

In 1 day, (A+B+C) together can do 1/10th of the work.

So, to complete one piece of work together, it will take 10 days.

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