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:
168 comments Page 7 of 17.
Zaidi said:
8 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.
Rapaka said:
1 decade ago
80%-----20 days.
100%------?
100%-20/80 = 25 days this is A work.
Now,
100%----25.
20%-----?
Answer 5 since it been done by A+B in 3 days 5x3 = 15 days.
If we subtract B from A+B that would be the answer.
1/15-1/25 = 4/150 = 2/75.
Hens option C.
100%------?
100%-20/80 = 25 days this is A work.
Now,
100%----25.
20%-----?
Answer 5 since it been done by A+B in 3 days 5x3 = 15 days.
If we subtract B from A+B that would be the answer.
1/15-1/25 = 4/150 = 2/75.
Hens option C.
Khan Singh John said:
9 years ago
A complete 80 work on 20 day then efficiency is 4.
A & B complete remaining 20 work in 3 days.
So A works 4*3=12 in 3 days.
12+80=92.
and B complete 8 works in 3 days.
and efficiency of B is 8/3.
Hence B will complete whole work in 100/(8/3) = 75/2.
A & B complete remaining 20 work in 3 days.
So A works 4*3=12 in 3 days.
12+80=92.
and B complete 8 works in 3 days.
and efficiency of B is 8/3.
Hence B will complete whole work in 100/(8/3) = 75/2.
Vishnu G said:
9 years ago
A alone completes the work in 25 days.
A and B together can complete the work in 15 days.
Let the total work be 75 units(LCM of 15 and 25).
i.e., A= 3 units /day ; A+B=5 units/day.
i.e.,B can do 2 units/day.
=> B alone can do the work in 75/2 days.
A and B together can complete the work in 15 days.
Let the total work be 75 units(LCM of 15 and 25).
i.e., A= 3 units /day ; A+B=5 units/day.
i.e.,B can do 2 units/day.
=> B alone can do the work in 75/2 days.
Sam said:
1 decade ago
Solution.
A's 1 day work = (80/100)*(1/20) = (1/25).
(A+B) 's 1 day work = (20/100)*(1/3) = (1/15).
So B's 1 day work will be (A+B) - (A).
B's 1 day work will be (2/75).
Hence 1 work will be completed by B alone in (75/2) days that's option C.
A's 1 day work = (80/100)*(1/20) = (1/25).
(A+B) 's 1 day work = (20/100)*(1/3) = (1/15).
So B's 1 day work will be (A+B) - (A).
B's 1 day work will be (2/75).
Hence 1 work will be completed by B alone in (75/2) days that's option C.
Seema duhan said:
1 decade ago
A = (1/20)*(80%) = (1/20)*(80/100) = 1/25. (EQUATION 1).
Remaining work=100%-80%=20%.
A+B=(1/3)*(20%)=(1/3)*(20/100)=1/15. (EQUATION 2).
Put equation 1 in equation 2, we get:
(1/25)+B = 1/15.
B = 2/75.
So B alone can do this work in 75/2 days.
Remaining work=100%-80%=20%.
A+B=(1/3)*(20%)=(1/3)*(20/100)=1/15. (EQUATION 2).
Put equation 1 in equation 2, we get:
(1/25)+B = 1/15.
B = 2/75.
So B alone can do this work in 75/2 days.
Vineela said:
8 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.
Supreeth said:
1 decade ago
St-1:
80%=20.
.'.(100*20)/80 = 25 days.
100%=?
St-2:
For 23 days A would have completed 23/25 part of the work,
St-3:
(25/25)-(23/25) = 2/25 part of work is completed by B in 3 days.
St-4:
.'. in 1 day (25/2)*3 = 37 1/2.
80%=20.
.'.(100*20)/80 = 25 days.
100%=?
St-2:
For 23 days A would have completed 23/25 part of the work,
St-3:
(25/25)-(23/25) = 2/25 part of work is completed by B in 3 days.
St-4:
.'. in 1 day (25/2)*3 = 37 1/2.
Win's said:
1 decade ago
80% work done by 20 day means 80/20 = 4% per day by A.
So 100/4 = 25 day for A.
He took B to do the remaining 20% task in three day.
Means A's contributions is 12% and B's 8% in three days.
So now B = 100/8*3 = 37.5 that's it.
So 100/4 = 25 day for A.
He took B to do the remaining 20% task in three day.
Means A's contributions is 12% and B's 8% in three days.
So now B = 100/8*3 = 37.5 that's it.
Suganya said:
1 decade ago
Simple method:.
A's one day work 80/20=4%.
A's three days work 12%.
The remaining work is only done by B in that three days=20%-12%=8%.
B's one days work=8/3%.
B completes 100% work in.
8/3% * x =100%.
So x=75/2=37.5.
A's one day work 80/20=4%.
A's three days work 12%.
The remaining work is only done by B in that three days=20%-12%=8%.
B's one days work=8/3%.
B completes 100% work in.
8/3% * x =100%.
So x=75/2=37.5.
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