Aptitude - Time and Work - Discussion

A and B can together finish a work 30 days.

They worked together for 20 days and then B left.

After another 20 days, A finished the remaining work.

ie, remaining work is 30 - 20 = 10.
10 work in 20 days.

So 1 work 2 days.
So 30 work in 30*20 = 60 days.

Why we can take t*d?

But some problems we can take pages/time.

(A + B) does a piece of work in 30 days.
Therefore (A+B) = 1/30.

Then (A+B) does the same work together for 20 days, so it is taken as 1/20 days.
Remaining work = 1/30 - 1/20 = 1/60 days.
1/60 = 60 days.

The whole work will be done by A = 60 days.

Why 1 is subtract from 2/3?

And what we do if the whole work was done by B alone. Then the answer should remain the same or will be changed?

Please answer me.

Its short tricks X * P/X - Y = 30 * 20/30 - 20 = 600/10 = 60.

A and B can complete the work in 30 days.

So 2 (1 unit by A and another 1 unit by B) units is completed per day.

30 * 2=60 is the total units completed in 30 days.

A and B together worked for 20 days and completed 20 * 2 = 40 units of work.

20 units are the remaining work to be done by A, only as B has left the job, so A's capacity is 1 unit a day so A takes 20 days to complete the job.

A can do a job completely by itself in 60 days as we know that it's capacity is 1 unit a day.

Don't stress, if both can complete a work in 30 days, it'll take 60 days for alone A to complete the job.

Here 2X equals 2 person i.e. A&B.

If 2X = 30days, X = 30days ÷ 2, ie X = 60days.

It may be A or B.

What is the answer if the question is " in how many days can B alone finish the work?

Pushpa can do a work in 10 days and Komal can do in 20 days. They work together for 5 days, then komal goes away In how many days more will Pushpa finish the work?

Can anyone solve this?