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 7 of 17.
Vishnu G said:
8 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.
Karan said:
2 years ago
A = 80% in 20 days.
80% = 80/100 = 4/5.
A = 4% Daily work.
80-100 = 20% of work remaining.
20% of work done by A+B in 3 days.
A = 4% Daily work in 3 days.
A = 4×3=12%.
20 - 12 = 8%.
B = 8%.
B = 8/100%×3 = 37.5 = 37 1/2.
80% = 80/100 = 4/5.
A = 4% Daily work.
80-100 = 20% of work remaining.
20% of work done by A+B in 3 days.
A = 4% Daily work in 3 days.
A = 4×3=12%.
20 - 12 = 8%.
B = 8%.
B = 8/100%×3 = 37.5 = 37 1/2.
(95)
Rajendra said:
1 decade ago
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..
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..
(2)
Ramya reddy said:
1 year ago
80% of the work in 20 days means 4/5.
100% he will complete in 25 days.
Now, the remaining 20% of the work in 3days means;
1-4/5 = 1/5 this is for one day
For 3days 3*1/5 = 1/15,
Now [1/15 - 1/25] = 2/75.
Rev= 75/2=37.5
100% he will complete in 25 days.
Now, the remaining 20% of the work in 3days means;
1-4/5 = 1/5 this is for one day
For 3days 3*1/5 = 1/15,
Now [1/15 - 1/25] = 2/75.
Rev= 75/2=37.5
(12)
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