Aptitude - Time and Work - Discussion

I didn't get step 1 how a 2 days work? I mean why we multiply with 2?

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"

First Two days work done by A = (1/20)+(1/20)=> 2/20=> 1/10.

Third day work done by A, B, C = (1/20)+(1/30)+(1/60)=> 6/60 => 1/10.
3 days work done: 1/5.

Then 1 day work done: (1/5)*(1/3) = 1/15.

So the answer is 115 days.

Let N be the total no.of days A has to work. So, a/q B and C works only for N/3 days. Total work = 1.

Therefore,

N*(1/20)+ (N/3)*((1/30)+(1/60)) = 1.

Solving this , you will get N = 15.

@Divya.

First Two days work done by A = (1/20)+(1/20)=> 2/20=> 1/10.

Third day work done by A,B,C = (1/20)+(1/30)+(1/60)=> 6/60 => 1/10.

Total work Done in 3 days= (1/10)+(1/10)=2/10 =>1/5.

Why we taken 1/10+1/10?

Here's a simple explanation :

WORK = (Rate)*(Time) ***time will cancel out***

First Day: Person A does all the work.

His working rate is 1/20 so (1/20)*1day = 1/20 work.

Second Day: Person A does all the work.

His working rate is 1/20 so (1/20)*1day = 1/20 work.

All in all in 2 days is 2/20 or 1/10.

Third Day: Person A is assisted by B and C.

(1/20)+(1/30)+(1/60) times 1 day = 1/10.

All in all in 3 days is (1/10)+(1/10)= 1/5 work is done.

So 4/5 remaining..

Question Says B and C assisted A EVERY third day.

Repeat the process until you get 5/5 or 1 full work that would be on the 15th day, A will complete 5/5 or 1 full work.

A's one day work is 1/20 ,

Therefore A's 2 day work will be (1/20)*2=(1/10),

Now (A+B+C)'s one day work will be = (1/20)+(1/30)+(1/60)=(1/10).

Since A is assisted on every third day of his work then total work done in three days will include A's 2 day's of work plus the work done on third day, that is (A+B+C)'s one day work,

Therefore work done in 3 days will be,A's two days work (1/10 )+ A,B,C's one day work (1/10)= (1/5).

Now in three days 1 out of 5 parts of work is done , and yet 4 parts are to be done there fore 4*3= 12 days and since we have calculated the earlier 1 parts requirement of days i,e 3 days total days will to finish 5 parts will be (12+3)= 15 days.

1/5 works is being done in 3 days.

i.e 1 of the 5 parts of work is done in 3 days.

So total there are 5 parts of work which will take 5*3=15 days.

There is confusion because the number is same for A working for 2 days (i.e.1/10 Days) and all three, A+B+C=1/10 days.

Hence its.

=2 working days of A 1/10+ All 3 together 1/10 days.

i.e. (1/10+1/10).