Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 9)
9.
A does 80% of a work in 20 days. He then calls in B and they together finish the remaining work in 3 days. How long B alone would take to do the whole work?
23 days
37 days
37
40 days
Answer: Option
Explanation:
| Whole work is done by A in |  |
20 x | 5 |  |
= 25 days. |
| 4 |
| Now, | |
1 - | 4 | |
i.e., | 1 | work is done by A and B in 3 days. |
| 5 | 5 |
Whole work will be done by A and B in (3 x 5) = 15 days.
| A's 1 day's work = | 1 | , (A + B)'s 1 day's work = | 1 | . |
| 25 | 15 |
 B's 1 day's work = |
|
1 | - | 1 | |
= | 4 | = | 2 | . |
| 15 | 25 | 150 | 75 |
| So, B alone would do the work in | 75 | = 37 | 1 | days. |
| 2 | 2 |
Discussion:
164 comments Page 6 of 17.
Atul said:
7 years ago
Thank you so much @Ganesh.
Zaidi said:
7 years ago
A's 1 day work = 80%/20 = 80/2000 = 8/200 = 1/25.
(A+B)'s 1 day work = 20%/3 = 20/30 = 2/30 = 1/15.
B's 1 day work = (A+B)' s 1 day work - A's 1 day work.
-> 1/15 - 1/25,
-> 2/75 = 1/n,
Days B need alone to complete the work = n.
-> 75/2 = 37.5.
(A+B)'s 1 day work = 20%/3 = 20/30 = 2/30 = 1/15.
B's 1 day work = (A+B)' s 1 day work - A's 1 day work.
-> 1/15 - 1/25,
-> 2/75 = 1/n,
Days B need alone to complete the work = n.
-> 75/2 = 37.5.
Zaidi said:
7 years ago
@Reya.
Take L.C.M of 15 and 25 which comes out to be 75.
Take L.C.M of 15 and 25 which comes out to be 75.
Reya said:
7 years ago
(1/15) - (1/25) how to simplify this?
Yash said:
7 years ago
We can solve it like this way also;
A do 80% of work in 20 days.
So,
A's one day's work = 80/100 * 1/20.
= 1/25.
Now A and B do remaining work in 3 days.
so we find remaining work and i.e. (1-1/25) = 24/25.
Now we multiply 24/25 by because of they(A and B) complete it in 3 days = 72/25 and the answer is 37 1/2.
A do 80% of work in 20 days.
So,
A's one day's work = 80/100 * 1/20.
= 1/25.
Now A and B do remaining work in 3 days.
so we find remaining work and i.e. (1-1/25) = 24/25.
Now we multiply 24/25 by because of they(A and B) complete it in 3 days = 72/25 and the answer is 37 1/2.
Akil Prakash said:
7 years ago
Well said @mayuri.
Abhik said:
7 years ago
A 80% done in 20 days 100% done in 25 days.
Another A+B done 20%in 3 days 100% in 15 days.
Now B = 25*15/10=37.5.
Another A+B done 20%in 3 days 100% in 15 days.
Now B = 25*15/10=37.5.
Vineela said:
7 years ago
Let total work is 100.
A did 80 work in 20 days,
1day work =80/20 =4 (A's efficiency),
A+B did 20 work in 3 days,
1 day work = 20/3 (A+B's efficiency),
4+B = 20/3,
B=8/3 (b's efficiency),
B's did whole work i.e 100 in = 100*3/8 = 37 1/2 answer.
A did 80 work in 20 days,
1day work =80/20 =4 (A's efficiency),
A+B did 20 work in 3 days,
1 day work = 20/3 (A+B's efficiency),
4+B = 20/3,
B=8/3 (b's efficiency),
B's did whole work i.e 100 in = 100*3/8 = 37 1/2 answer.
Shree said:
8 years ago
Thanks for the explanation.
P srinivas Rao said:
8 years ago
A 80, of work = 80/100= 4/5 = 1/5.
A 100, of whole work = 100/80*20=25.
remaining work (A+B)= 1/5= 3days.
(A+B) total work= 3*5/1= 15 days.
B whole work= 25*15/10=37.5 answer.
A 100, of whole work = 100/80*20=25.
remaining work (A+B)= 1/5= 3days.
(A+B) total work= 3*5/1= 15 days.
B whole work= 25*15/10=37.5 answer.
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