Aptitude - Time and Work - Discussion

Sorry I can't get it why we should multiply with that 5/4 ?

A did only 80% of work out of total work in 20 days so
work done by A=80/100=5/4
so total workdone by A=20*5/4

How do we get that A & B together can do work in 15 days?

@shefali..the 15 days is nothing but remaining work probability. 4/5 i.e 80% work is done by A so remaining is 1-(4/5)= 1/5. its same like p+q=1 in probability.
n same like 3*5=15 days

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

A does 80% in 20 days..so
A does 100% in 25 days..
A's 1 day work=1/25
A+B does 20% in 3 days..so
A+B does 100% in 15 days
A+B's 1 day work=1/15
1/25+B=1/15
B=1/15-1/25
B,s 1 day work=2/75
so B,s work=75/2 i.e 37 1/2 days..

Thank you very much rajendra.

@Baskar you have done great job. Just carry on.