Aptitude - Time and Work - Discussion

@vikas.

Superb explanation. :-).

Why we take 2 days? Please help.

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.

1/20+1/(30X3)+1/(60X3) = 1/15
Is my way of solving correct?

@Vishnu...

As per the statement A will do the work three days continuosly but only on third day B & C will assist, so
A's thrid day work must also include with both B & C
that's why...
(A + B + C)'s 1 day's work is taken

How it is user
Now, 1 work is done in 3 days.
5
Whole work will be done in (3 x 5) = 15 days.

How you got 6/60?

I think the answer is 12.

Why you have taken the a+b+c? A is assisted by only B, C know.

Why are you taking 2 days for first step?

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