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.
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.
Juanita said:
1 decade ago
My understanding is that A alone does 80% work which is 5/4. Remaining 20% work is done by A & B which is 1/5.
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.
Himanshu gawande said:
1 decade ago
A's 1 day work (1/80%)x20 = 25 days.
Srini said:
1 decade ago
A's 20% work in 5 days and A+B'in 3 days,
So B's 20 work in (1/3 - 1/5) = 2/15 i.e 15/2.
So B's 100% work in (15/2)*5 = 75/2 = 37.5 days.
So B's 20 work in (1/3 - 1/5) = 2/15 i.e 15/2.
So B's 100% work in (15/2)*5 = 75/2 = 37.5 days.
Gaurav gupta said:
1 decade ago
Here is the solution to get total work days of A.
80% work can done in 20 days.
So 1% can be done in (20/80%) = (20/80)*100 = 25 days.
80% work can done in 20 days.
So 1% can be done in (20/80%) = (20/80)*100 = 25 days.
Aravind said:
1 decade ago
For A 80% of work = 20 days.
100% of work = x?
Cross multiple:
x = 20*100/80.
x =25 days.
A 1 days work = 1/25....(1).
For a and b together 20% of work = 3 days.
100% of work = x?
Cross multiple x = 15 days.
A 1 day work + b 1 day work = 1/15.
1/25+ b 1 day work = 1/15.
B 1 day work = 1/15-1/25 = 2/75.
B Can complete in 75/2 = 37 1/2.
100% of work = x?
Cross multiple:
x = 20*100/80.
x =25 days.
A 1 days work = 1/25....(1).
For a and b together 20% of work = 3 days.
100% of work = x?
Cross multiple x = 15 days.
A 1 day work + b 1 day work = 1/15.
1/25+ b 1 day work = 1/15.
B 1 day work = 1/15-1/25 = 2/75.
B Can complete in 75/2 = 37 1/2.
Sonam said:
10 years ago
My method:
A's one day work = 80/100*1/20 = 1/25.
A+B together = 20/100*1/3 = 1/15.
B's one day work = (A+B)-A.
1/15-1/25 ---> now take LCM and solve.
You will get 2/75 i.e., 75/2 days.
Hope this helps you.
A's one day work = 80/100*1/20 = 1/25.
A+B together = 20/100*1/3 = 1/15.
B's one day work = (A+B)-A.
1/15-1/25 ---> now take LCM and solve.
You will get 2/75 i.e., 75/2 days.
Hope this helps you.
Kannan said:
10 years ago
I don't understand please explain.
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.
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