Aptitude - Time and Work - Discussion

Discussion Forum : Time and Work - General Questions (Q.No. 4)
4.
A is thrice as good as workman as B and therefore is able to finish a job in 60 days less than B. Working together, they can do it in:
20 days
22 1 days
2
25 days
30 days
Answer: Option
Explanation:

Ratio of times taken by A and B = 1 : 3.

The time difference is (3 - 1) 2 days while B take 3 days and A takes 1 day.

If difference of time is 2 days, B takes 3 days.

If difference of time is 60 days, B takes 3 x 60 = 90 days.
2

So, A takes 30 days to do the work.

A's 1 day's work = 1
30

B's 1 day's work = 1
90

(A + B)'s 1 day's work = 1 + 1 = 4 = 2
30 90 90 45

A and B together can do the work in 45 = 22 1 days.
2 2

Discussion:
281 comments Page 6 of 29.

Ashirwad dubey said:   1 decade ago
Hi friends
k*x/(k^2-1)
k=3
x=60 given in que
ok friends

ASHIRWAD said:   1 decade ago
HI FRIENDS THIS IS THE simplest method for solving this type of que....
K*S/(A^2-1)

where S=DAYS FOR FINISHING WORK(60 GIVEN IN QUE)
K=3 GIVEN IN QUE

Vikas said:   1 decade ago
I didnt understand how did we get that (3/2)*60 ?

Showry said:   1 decade ago
Hi Friends,

A:B=1:3 time taken.........since A is 3 good as B

A takes 60 days less than B
B-60:B=1:3............
i.e B-60/B=1/3..... B=90 days.... A=30......

(A+B)'s one day work (1/30+1/90) = (2/45)

Total work by (A+B) is 45/2 i.e 22 1/2.............

Gowri said:   1 decade ago
kl/(k)^2-1
k=3
l=60
3*60/(3)^2-1
=45/2
=22.5

Nagarjun said:   1 decade ago
@Vikas

Its just cross multiplication.
If the difference is 2 days then b takes 3 days
If the difference is 60 days then b takes x days

Hence, x= (60*3)/2.

I think you got it now.

Naresh kumar said:   1 decade ago
Thank you guys.

Malini said:   1 decade ago
Sheetal thanks a lot dear. This short cut is very much easy.

Baskar said:   1 decade ago
@bharathi
i think u r in confusion..
just know dat
work = day..
1 day = 2/45 works..
in ques ask abt "work"?
den cross mul
1 work = 45/2 days..
now u got it

G.P. said:   1 decade ago
SIMPLE AND BEST WAY
since a is thrice better than b
hence a:b=1:3
similarly a takes 60 days less than b
hence a:b=(b-60):b=1;3
cross multiplication n we get
3b-180=b hence b=90days hence a=30days
1/90+1/60=4/90 hence total daysreciprocal 90/4=45/2


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