Aptitude - Time and Work - Discussion

We are also do this,

x = 40days = 100%
For 8 days = ? (20%) so, 80% works remaining. That is done by y in 16 days.
80% = 16days
100% = ? (20days)

(x + y)'s 1 day work = (1/40) + (1/20).
= (3/40).
= (40/3) = 13*1/3.

I am not sure about this answer but changing 4/5 to 5/4 could be because we are finding complete work for Y.

In other problems where same fractions were calculated, there we were finding remaining work. Here for Y, we are finding the Whole work. This could be the reason though I am not sure.

I still can't get the 4/5 converted to 5/4. In some of the previous sums it was not converted then why here?

Ok thank you friends I understood.

The main reason for 16*5/4 is unitary method. It goes like this:

It takes 4/5 work to completed by C = 16 days.

So for 1 work it will take: 16*5/4.

How to solve using LCM method?

x's speed of work is 40, so work in 1 day is 1/40.

x does 8 days and leaves, so work done is 8*(1/40) = 1/5.

x does only 1/5 of the work , so remaining work to be done is 4/5 (1-1/5 = 4/5).

y's speed of work is not given, let us take it as 'K'. but he completes the remaining 4/5 work in 16 days.

So 16*(1/K)=4/5 which gives K = 20.

Now both together takes ( x speed of work + y speed of work).

1/40 + 1/20 = 3/40 = 1/(40/3) = 1/(13 1/3).

So the ans is 13 1/3.

X's 1 day work 1/40 ? how ?

Ya we can't get. The remaining work of y is 4/5. But it taken has 5/4.

Can't get it because what does it mean of 16*5/4?