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.
Atyanand said:
10 years ago
A complete 80% work in 20 days.
So A complete 100% work in 25 days.
Work done by A in 1 day = 1/25......equation (1).
A+B complete 20% work in 3 days.
So, A+B complete its 100% work in 15 days.
Work done by A+B in 1 day = 1/15.
From equation 1.
B = 1/15-1/25 = 2/75.
So A complete 100% work in 25 days.
Work done by A in 1 day = 1/25......equation (1).
A+B complete 20% work in 3 days.
So, A+B complete its 100% work in 15 days.
Work done by A+B in 1 day = 1/15.
From equation 1.
B = 1/15-1/25 = 2/75.
VATHSA said:
3 years ago
80% in 20days.
100% in ? ==>25 days.
A's work per day = 1/25,
A completes 80% of work = remaining 20% of work = 20/100 of 1 = 1/5.
Together they complete in 3 days.
(1/25 + 1/B) *3= 1/5
SOLVE:
1/B = 2/75 = B's work per day.
For B to complete = 75/2 = Answer.
100% in ? ==>25 days.
A's work per day = 1/25,
A completes 80% of work = remaining 20% of work = 20/100 of 1 = 1/5.
Together they complete in 3 days.
(1/25 + 1/B) *3= 1/5
SOLVE:
1/B = 2/75 = B's work per day.
For B to complete = 75/2 = Answer.
(23)
Raaj said:
1 decade ago
80% = 120.
100% = 150.
A can do 120 unit in 20 days.
A can do 1 day = 120/20 = 6 unit.
Remaining 150- 120 = 30.
A+B can do 30 unit in 3 day.
A+B can do in 1 day = 30/3 = 10 unit.
A+ B = 10 unit.
A = 6 unit.
B = 10 - 6= 4 unit.
B can alone do = 150 / 4 = 37 1/2.
100% = 150.
A can do 120 unit in 20 days.
A can do 1 day = 120/20 = 6 unit.
Remaining 150- 120 = 30.
A+B can do 30 unit in 3 day.
A+B can do in 1 day = 30/3 = 10 unit.
A+ B = 10 unit.
A = 6 unit.
B = 10 - 6= 4 unit.
B can alone do = 150 / 4 = 37 1/2.
Yogesh said:
1 decade ago
My method:
A's 1% work done time = 80/20 = 4%.
Means in 1 day a completes 4%......(1).
Now,
A+B 1 day work = 20/3.
B work = 20/3 - 4/1 = 8/3.
B work in 1 day = 8/3 ---- (2).
So now,
For 100% work by B is:
8/3*1/100 = 300/8 = 37.5 days. work
Answer..(:
A's 1% work done time = 80/20 = 4%.
Means in 1 day a completes 4%......(1).
Now,
A+B 1 day work = 20/3.
B work = 20/3 - 4/1 = 8/3.
B work in 1 day = 8/3 ---- (2).
So now,
For 100% work by B is:
8/3*1/100 = 300/8 = 37.5 days. work
Answer..(:
Ravi said:
5 years ago
A do 80%work for 20days.
(Simplify it remaining 20%do in 5days).
Now work for 20%is 1/5 and work are done by both a+b is 1/3. Do lcm we get 15 and subtract 5-3/15=2/15.
Now it is 20% of work done by B is 2/15.
Now 20%*5=100% i.e,2/15*5=2/75 ans is 37 1/2 days.
(Simplify it remaining 20%do in 5days).
Now work for 20%is 1/5 and work are done by both a+b is 1/3. Do lcm we get 15 and subtract 5-3/15=2/15.
Now it is 20% of work done by B is 2/15.
Now 20%*5=100% i.e,2/15*5=2/75 ans is 37 1/2 days.
Ajith said:
1 decade ago
1) 100*20/80 =25.
2) Total work done in 25 days.
3) Remaining work finished in 5 days.
4) If A&B work together 3*5=15.
5) A's one days work 1/25.
6) A+B one days work 1/15.
7) 1/15 - 1/25 = 4/150= 2/75.
8) So B alone would do the work in 75/2= 37 1/2.
2) Total work done in 25 days.
3) Remaining work finished in 5 days.
4) If A&B work together 3*5=15.
5) A's one days work 1/25.
6) A+B one days work 1/15.
7) 1/15 - 1/25 = 4/150= 2/75.
8) So B alone would do the work in 75/2= 37 1/2.
Sudheer said:
1 decade ago
A's 80% work i.e 4/5 work = 20 days.
Therefore 1 work = 20x5/4 = 25 days.
Similarly, (A+B) 's remaining work i.e 20% work==>1/5 work = 3 days.
Therefore 1 work = 5x3 = 15 days.
We got A = 1/25.
And A+B = 1/15.
Solve above equations we will get B = 75/2.
Therefore 1 work = 20x5/4 = 25 days.
Similarly, (A+B) 's remaining work i.e 20% work==>1/5 work = 3 days.
Therefore 1 work = 5x3 = 15 days.
We got A = 1/25.
And A+B = 1/15.
Solve above equations we will get B = 75/2.
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.
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:
8 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.
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