Aptitude - Time and Work - Discussion

A's 1 day's work =1/15.
B's 1 day's work =1/20.
(A + B)'s 1 day's work = (1/15 + 1/20) = 7/60.
(A + B)'s 4 day's work = 4 * (7/60) = 28/60.
In 4 days they complete 28 parts of work out of 60 parts of work.
Rest of work is 32 parts.
:=> 32/60 has to be completed i.e 8/15.

A one day work = 1/15.
B one day work = 1/20.
One day work of both = 1/15 + 1/20 = 7/60.
4days work of both = 7/60 * 4 = 7/15 is the total work of 4days.
So, remaining days work = 1 - 7/15 = 8/15.

Hence, 8/15 answer.

Good, thanks @Billal Hossin.

@All.

According to me, it can be solve by 2 methods.

Method- 1:
A's 1 day work = 1/15.
B's 1 day work= 1/40.

(A+B)'s 1 day work= (1/15)+(1/40).
= (8+6) /120.
= 14/120.
= 7/60,

(A+B)'s 4 days work= (7*4)/600,
= 7/15,

Left work is= 1- (7/15 ),
= 8/15 (Ans).

Method-2:
(A+B)'s 4 days work= (4/15)+(4/20),
= (4/15)+(1/5),
= 7/15.
Left work= 1- (7/15).
= 8/15 (Ans).

A=15 Days.
B=20 Days.

LCM 60.
A's 1 Day work=4.
B's 1 Day work=3.

Both together 1 Day work= 7/60.
Both together 4 Days work= 28/60.

Rest work= 32/60 = 8/15.

Can you explain why you have put 1_7/15?

A=1/15 and b=1/20 ,a+b=7/60*4 =7/15 so,
1-7/15 = 8/15.

A' work is (1÷15) in one day,
B's work is (1÷20) in one day,

If both perform the work together then (1÷15)+(1÷20)=(35÷300) work is done in one day.
Now multiplying it by 4 so we get the amount of work done in 4 days.

(35÷300)*4 = (7÷15).
Now we know the total amount of work is 1.

Then subtract (1)-(7÷15)=(8÷15) the remaining work.

By considering LCM 60 in that case why should we need to do remaining work divided by total work.

We know A done his work in 15 days and B in 20 days so total work is we take as 1.work is inversely proportion to days 1÷15 +1÷20=(15+20)/15x20=35/300=7/60=7x4/60=28/60=1-28/60=8/15.

Here 1 indicates total work.