Aptitude - Time and Work - Discussion

hey pls tell clearly ya its quite confusing

For all friends..
work = days

for A:
80% work = 20 days
4/5 work = 20 days
cross mul
1 work = 5/4 * 20 days
1 work = 25 days
A's 25 days = 1 work ----------------------------->1

A+B remain work done in 3 days
total work = 1
80% work = 4/5
100% work = 1
100% - 80% = 1 - 4/5 = 1/5

for A+B:
work = days
1/5 work = 3 days
cross mul
1 work = 15 days
dat is

A+B's 15 days = 1 work --------------------------->2

now we know A's and A+B's work
now find B's work
apply A's in A+B's
A+B 1 Days= 1/15 works
A's 1 days = 1/25 works---->from 1..

1/25 + B = 1/15 works
B's days = 1/15 - 1/25 Works
B's days= 2/75 works
we have to calc works
cross mul
B's work = 75/2 days = 37 1/2 days

@ baskar: thanks dude

For A
Here 80% work is done by A in 20 days.
so 80/20 = 4% work per day.
So,remaining 20% will take 20/4= 5 days.
so A will take 20+5= 25 days to complete 100% of work.
so A's 1 day work is 1/25 --------------(1)


---------------------------------------------------------
Similarly, remaining 20% is done by both (A & B) in 3 days.
so (20/3)% work per day.
Now, 100% work will be completed in 100/(20/3)
i.e. 100 x 3/20 =15 days.
(A + B)'s one day work is 1/15.
So,
A + B = 1/15
1/25 + B = 1/15
B = 1/15 - 1/25
SO B's one day work = 4/150 = 2/75
So B will take 75/2 days. i.e. 37 1/2 days.

thankx rajendra.........

Great explanation by baskar. Thanks.

Hi Guys,

General Concept: Time and work

A can complete work in X days
1.e., A can complete 100% of work in X Days

A's 1 day work = (Amount of work completed) /(number of days)
so,
A's 1 day work = 100%/X => 100%(1/X)

Now,

A completed 80% of work in 20 Days
so, A's 1 day work = 80%/20 => 1/25

A+B completed 20% of work in 3 days
so, (A+B)'s 1 days work = 20%/3 => 1/15

A+B = 1/15
B = (1/15-1/25) => 10/375

B's 1 day work = 100%/(10/375) => 100%(375/10)

B alone completed 100% of work in 375/10 Days

B = 37.5 Days => 37 1/2 Days

Easy Method:-

A does 80% work in 20 days= 80%/20=80/100*1/20 =1/25...(i)

A and B togheter finish the remaining work(which is 20%) in 3 days.
so (A+B) do 20% work in 3days= 20%/3=20/100*1/3 =1/15....(ii)

Now we hv to find B's Work days

So subtract equ. (ii) from (i)

(A+B)-A =1/15-1/25
B =2/75
B =37 1/2 DAYS

In 20 days A does 80% work. So in one day =80/20=4%

Let we start from sunday then S M T W T F S....4% each day then total 25 days will be taken by A to 100% work done .

Similarly for A+B, in 3 days (100-80)=20% work done. for one day=20/3%..so for 100% counting on each day 15 days will come

So a+b=1/15=>b=1/15-1/20=>2/75

Howz 80/100=5/4?