Aptitude - Time and Work - Discussion

For A:-
15 days for 1 job
in 1 day 1/15 (part of the one job)
for B:-
20 days for 1 job
in 1 day 1/20 (part of the one job)
FOR BOTH IN ONE DAY:-
1/15+1/20=7/60
FOR BOTH IN 4 DAYS:-
(7/60)*4=7/15(THEY HAVE DONE)
THE REST PART OF THE JOB IS:-
1-(7/15)=8/15 (ANS)

We can solve this problem by another way also..let us see..

A can do a work in 15 days
B can do a work in 20 days
Take LCM for 15 & 20 i.e Total work = 60

Then,
A's capacity = 60/15 = 4
B's capacity = 60/20 = 3
They work together for 4 days,

Then, A's capacity + B's capacity = 4 + 3 =7
AB's one day capacity = 7
since they work for 4 days, they have done 4x7 =28 work
Work left = Total work - work done by AB
= 60 - 28 = 32
Remaining work / total work = 32 / 60 = 8 / 15

This method will take less time to compute guys...please try it.

Thanks all.

Why (1 - 7/15)?

@sundar.

Good explanation.

Can you explain how 7/60 came?

We have to calculate the remaining work after 4 dayz ,so why we subtract 1 dayz work from 4 day work? plz clear the question.

7/60 x4 =7/15 please explain me

@Poorni:

Why 1-(7/15)?

We consider the total work as 1.

The amount of (work done) is 7/15.

Subtract the total work by the work done we will get the amount of work to be done

That is why we use 1-(7/15).

Hope this help you.

@Prkash.

Superb explaination.