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 12 of 17.
Reya said:
7 years ago
(1/15) - (1/25) how to simplify this?
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.
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.
Atul said:
7 years ago
Thank you so much @Ganesh.
Mayur said:
7 years ago
80% work --> 20 Days, Then
100% work --> ?? Days.
i.e 20 * 100/80 = 25.
Similarly (remaining work) = 20% work done in 3 days that means 100% work done in 15 Days.
Now
1/25+B = 1/15,
1/15-1/25 = B,
2/75,
37.5.
100% work --> ?? Days.
i.e 20 * 100/80 = 25.
Similarly (remaining work) = 20% work done in 3 days that means 100% work done in 15 Days.
Now
1/25+B = 1/15,
1/15-1/25 = B,
2/75,
37.5.
Dhyey said:
6 years ago
Thank you @Mayuri.
Shivaputra said:
6 years ago
@ Rajendra.
Thanks for the clear explanation.
Thanks for the clear explanation.
Harish said:
6 years ago
80% is completed so remaining is 20% work.
This 20% work is completed by A&B together in 3 days,
If 20% is 3 days then 100% is 15 days,
A completed 80% in 20days then A can complete 100% in 25 days,
So B's work =1/15 -1/25 =2/75,
2 work in 75 days,
1 work in 75/2 days,
= 37 1/2 days.
This 20% work is completed by A&B together in 3 days,
If 20% is 3 days then 100% is 15 days,
A completed 80% in 20days then A can complete 100% in 25 days,
So B's work =1/15 -1/25 =2/75,
2 work in 75 days,
1 work in 75/2 days,
= 37 1/2 days.
Vijay said:
6 years ago
1day work of A : (1/20)*80/100 = 1/25,
A+B = 3/25 + 3/x=1/5(for 3days).
Find x = 37.5.
A+B = 3/25 + 3/x=1/5(for 3days).
Find x = 37.5.
Harivishnu said:
6 years ago
Thanks @Harish.
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