Question

3
3. If A and B can do a piece of work in 12
days, B and C can do it in 15 days and C
and A can do it in 20 days. In how many
days A, B and C can complete the whole
work, working together?​

Answer 1

Answer:

LCM(12,15,20)=60

Now this 60 units can be treated as the total work and we will now calculate the one day work

One day work of A and B = 60/12 = 5 units

One day work of B and C = 60/15 = 4 units

One day work of C and A = 60/20= 3 units

Now if we add all three we get:-

2(A+B+C)=12 units

So one day work of A, B and C put together is 12/2 = 6 units

To find one day work of A:-

One day work of A, B and C together minus one day work of B and C, that is 6–4=2 units

If the total work is of 60 units and the one day work of A is 2 unit, then alone A needs 60/2 = 30 days to finish the work.

The same way we can find the number of days required by B and C to finish the work by themselves.