Question

P alone
can do
a piece of work in 12 days
and a can do it in 7.5 days In how
many days o alone do the same work?
​

Answer 1

Answer:

A and B together can finish a piece of work in 12 days. If A alone can finish the same work in 20 days, then in how many days will it take B to finish alone?

A can do a work in = 20 days

Let B can do the work in =X days

Both A and B can do the work in = 1/12 days

Therefore 1/20 + 1/X= 1/12

So 12 (X+20) = 20 X;

So 8X= 240 ; X= 30.

Therefore “B” can do the work alone in 30 - days.

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Another Simple Method:

In 12- days A- can complete= 12/20= 3/5- part of the work.

So in 12- days B- can complete (1–3/5) = 2/5- part of the work.

So complete work can be done by B- alone in 12÷ (2/5)= 12 x5/2= 30- days.

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