Aptitude - Time and Work - Discussion

Can anyone say why we are multiplying 20 with 5/4?

80% of work will be completed int 20days. ie) 80/100 = 4/5.
Remaining 20% of work ie, 20/100 = 1/5.

A can do 100 % of work in 25 days,
So A's per day work is 1/25.

Now A+B together do the 20% of work.

(A + B) work = 3 days.
1/5 work = 3 work days.
1 work = 5 * 3 days,
Work = 15 days.

(A+B) per day work is = 1/15,
A's per day work is 1/25,
Now A + B = 1/15,
1/25 + B = 1/15,
B = 1/15 - 1/25,

B alone = 75/2 ie. 37 1/2 days.

Hey guys 80/100 = 4/5 then why you people multiplying 5/4 * 20?

The total work is 100 unit.

A can do 80 unit in 20 days. So he can do 4 unit in 1 days.

Now A has finished 80 units so remaining work is 20 unit.

So, 20 unit work takes 3 days time to complete in which A will do 12 unit.
(since A do 4 unit/days).

Thus, B do 8 unit in 3 days.
And total work is 100 unit so B will take (3/8) * 100 = 37.5 days to complete total work.

==>> A can do 80% W ---------> 20 days.

=> Then, 100% W ---------->

=> How many days(D), By Cross-multiplying we get,

D = (100*20)/80 ==> D = 25.

i.e., A can do 100% of the work in 25 days.

So, A's 1 day work, i.e., 1/A = 1/25 -----------------------(1)

The remaining work is 20%.

==>> Given A+B can do the 20% W --------> 3 days.

=> Then, 100% W ------------------------>

=> How many days(D), By cross-multiplying we get,

D = (100*3)/20 ==> D=15.

i.e., A+B can do 100% of work in 15 days.

So, A & B one day work i.e., 1/A + 1/B = 1/15 -----(2)

Solving 1 & 2, we get B's 1-day work as 1/B = 2/75.

So,

B alone would take to do the whole work i.e., B = 75/2 = 37(1/2) days.

Too good @Baskar.

Thanks for explaining the answer.

A does 80% of work in 20 days.

Then A can do 100% of work in 25 days and 20% of work in 5 days.
A + B together finish the remaining 20% of work in 3 days.

For 20% of work B alone:
3/5 + 3/x = 1.
x = 7.5 days.

For 20% of work B alone takes 7.5 days then for 100% of work B takes,
20% = 7.5.
100% = ?.
100 * 7.5/20 = 37.5 = 37 1/2.

Hi, one easy and time-saving method is:

A done 80% work in 20 days.
So, one day work of A is = 80/20 = 4%.

Here, remaining work is = 100 - 80.
=20%.

A and B both together remaining work and they take 3 days to accomplish it.

During this three day, A's work is = 4% * 3 = 12%.
Then, B's work during 3 days = 8%.

Work - Days.
8% - 3.
100% - (?).

100 * 3/8 = 300/8 = 37.5 days.

Hi all,

Work Completed = 80% = 80/100 = 4/5.

So, Remaining = 1- 4/5 = 1/5.

A + B complete this in 3 days so if they had continued total time required will be 5 * 3 = 15 days.

A individual complete it in 5/4 * 20 = 25 Days.
Then, B individual 1 day Work = 1/(A + B) - 1/A = 1/15 - 1/25 = 2/75.

So, B will complete whole work in 75/2 = 37 1/2.

Now I understand this concept.