A and Bcan do a piece of work in 12 days, B and C in 15 days, C and A in 20 days then the number of days taken by A, B and C together to finish the work are:

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10 days

12 days

14 days

15 days

answer is A.

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Detailed Solution

Concept- Before moving on, it is important to understand the following requirement: the amount of work completed is always directly proportional to the number of days needed. When all of the aforementioned situations are added together, we can see that A, B, and C all appear twice, indicating that the sum of these three equations equals the amount of work completed by A, B, and C over the course of two days. Next, divide the total amount of work completed by A, B, and C in one day by 2.
Given A and B do piece of work in 12 days and B and C in 15 days and C and A in 20 days
Then

and

one day work

And B and

one day work

And

and

one day work

Then A,B and C two days work Question Image

Then

and C one days work

So A, B and

do work in 10 days
Hence, the correct answer is option 1) 10 days