Aptitude - Time and Work - Discussion

Answer Explained:

A is working alone for two days, 3rd day he is assisted by B and C.

A's 1 day work=1/20
A working on 2 days=2*1/20=1/10

A+B+C working on 3rd day, so 1 day of working together=1/20+1/30+1/60=6/60=1/10

So total work done till 3rd day=1/10+1/10=2/10=1/5
So if in 3 days = 1/5 of work is completed....
Than, 3*5 days = 1/5*5 work will be completed.
=15days

Solution:

A do a piece of work in = 1/20 days.
'A' work alone for 2 days, so the work done by A on the second day is = 2/20 = 1/10
On the third day, A is assisted by B&C, then the work done by three of them is = 1/10 + 1/20 + 1/30 = 3/20.

Total work done by A in 3 days is = 1/20 + 3/20 = 1/5.

As we have to find number of days, so,

1/5 part of work done by A is in = 3 days.
1 part of the work done by A is in = 3x5 = 15 days.

In 15 days, A can do the work if he is assisted by B& C on the third day.

@Dhanam.

Because on third day they are doing combined work it means that for 1st 2 days they have worked alone here in question. About A has asked so he is doing only A.

A's 2 day's work = (1/20x2) = 1/10.

(A + B + C)'s 1 day's work = [(1/20)+(1/30)+(1/60)] = 6/60 = 1/10.

Work done in 3 days = [(1/10)+(1/10)] = 1/5.

Now what they ask "How many days can "A" do the work?"

Here revise the FORMULA NO:2.

That is:

Days from Work:

If A's 1 day's work =1/n,then A can finish the work in n days.

Here ===> [1 DAY's work = NO.of WORK / required "n" Day's do the work ].

We want no.of DAY's;

So rearrange the formula; we get,

No.of WORK = (1DAY's work * "n" DAY's) ------> take eqn no.1.

Now, (1/5) work is done in 3 days.

3 = 1/5.

So apply above the data's in eqn no.1.

1(No.of Work) = (Day's of Work )3 * ("n" DAY's)5.

1(No.of Work) = 15 Day's

So "A" is require 15 Day's to do a 1 work.

"I HOPE U WILL B UNDERSTAND"

How do you know total working day is 3 (last step).

3 days work = 1/5
it means 1 day work =1/15
that is 1/15 work is done in 1 Day
now 4/5 part of work that is (1-1/5) will be done in :15*4/5 =12 days....
Hence total work done will done in (12 + 3 ) days...

There's a simple logic friends,

If a person wrks for n days, his 1 day's work is 1/n.
or the other way round,
if 1/n is the 1 day's work then he works for n days.
& it can be very well known if 1 day's work is known it can be multiplied with any numbers of days you wish to.

Similarely,

Here last statement tell the same i.e. 3days work is 1/5,
so to calculate 1 day's work we need to divide it by 3 wiz gives 1/15.
so if 1/15 is 1 day's work then they together work for 15 days.
& the logic behind 2 days & 3 dats work is :
A's 2 days work is (1/20)*2, i.e 1 day's multiplied by nth day.

but on the "3rd day" they all A,B&C work together wiz equals to 1/10.

Therefore 2 days + 3rd day's wrk gives 3 day's work.

Here my simple ans:

A is working continue 2 day's.So he's 2day's work is:1/20*2=1/10;

in 3rd day he join other two person B and C.So here 3 member work:

1/20+1/30+1/60=1/10;

3 day's work is :1/0+1/10=1/5

So total work done by them is 10+5=15;

i.e;

3 days =1/5

6 days=2/5

9 days=3/5

12 days=4/5

15 days=5/5(1)==work completed

Guys check dis out........
as we know A will be assist by B & C every third day, so first two day A will work again
A's 1st day of work = 1/20
A's 2nd day of work = 1/20
(A+B+C)'s 3rd day of work = 1/20+1/30+1/60=1/10
total work of 3 days = 1/20+1/20+1/10=1/5
hence,
3 days of work = 1/5
1 day of work will be=1/5*3
=1/15
so work will complete in 15 days