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 4 of 17.
Manjunath deepak said:
8 years ago
A can do 80% of work in 20 days which means that he can do 100% work in 25 days.
A and B together can do 20% work in 3 days which means that they can do 100% work in 15 days.
Now,A's 1 day work=1/25--------->1/A=1/25.
(A+B)'s 1 day work=1/15------> (1/A)+(1/B)=1/15.
From the above two equations,(1/25)+(1/B)=1/15 which gives 1/B=2/75.
-->B=75/2=37.5.
A and B together can do 20% work in 3 days which means that they can do 100% work in 15 days.
Now,A's 1 day work=1/25--------->1/A=1/25.
(A+B)'s 1 day work=1/15------> (1/A)+(1/B)=1/15.
From the above two equations,(1/25)+(1/B)=1/15 which gives 1/B=2/75.
-->B=75/2=37.5.
Jyoti said:
8 years ago
A does 80% work means 80÷100 =4/5 work in 20 days.
So, A's 1 day work = 4/5 * 1/20 = 1/25 work in 1day.
Now, It is said that A+B can do a piece of work in 3 days.
Therefore remaining work =1 - 4/5 = 1/5.
So, A+B's 1day work = 1/5 * 1/3 = 1/15.
Now work done by B in 1 day = 1/15-1/25 = 2/75.
Therefore B can do whole work in 75/2.
Hope it is clear to you!
So, A's 1 day work = 4/5 * 1/20 = 1/25 work in 1day.
Now, It is said that A+B can do a piece of work in 3 days.
Therefore remaining work =1 - 4/5 = 1/5.
So, A+B's 1day work = 1/5 * 1/3 = 1/15.
Now work done by B in 1 day = 1/15-1/25 = 2/75.
Therefore B can do whole work in 75/2.
Hope it is clear to you!
Surekha Merla said:
5 years ago
Let's take 5 parts total.
A finishes 80% of it in 20 days, A can finish whole work in 25 days.
A one day work is 1/25.
A= 4/5 work in 20 days.
Remaining, 1-(4/5)= 1/5 part.
(A+B)= 1/5 work in 3 days.
A's 3 days work = 3/25.
Therefore,
For 3 days, A+B= 1/5.
(3/25)+B= 1/5.
B= 2/25 in 3 days.
B's one day work, 2/75 work.
Whole work by B= 75/2.
B = 37 1/2 days.
A finishes 80% of it in 20 days, A can finish whole work in 25 days.
A one day work is 1/25.
A= 4/5 work in 20 days.
Remaining, 1-(4/5)= 1/5 part.
(A+B)= 1/5 work in 3 days.
A's 3 days work = 3/25.
Therefore,
For 3 days, A+B= 1/5.
(3/25)+B= 1/5.
B= 2/25 in 3 days.
B's one day work, 2/75 work.
Whole work by B= 75/2.
B = 37 1/2 days.
Bharath said:
8 years ago
Work done by A in 20 days = 80/100 = 8/10 = 4/5
Work done by A in 1 day = (4/5) / 20 = 4/100 = 1/25 --- (1)
Work done by A and B in 3 days = 20/100 = 1/5 (Because remaining 20% is done in 3 days by A and B)
Work done by A and B in 1 day = 1/15 ---(2)
Work done by B in 1 day = 1/15 " 1/25 = 2/75
=> B can complete the work in 75/2 days = 37 (1/2) days.
Work done by A in 1 day = (4/5) / 20 = 4/100 = 1/25 --- (1)
Work done by A and B in 3 days = 20/100 = 1/5 (Because remaining 20% is done in 3 days by A and B)
Work done by A and B in 1 day = 1/15 ---(2)
Work done by B in 1 day = 1/15 " 1/25 = 2/75
=> B can complete the work in 75/2 days = 37 (1/2) 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.
Parvin Kumar said:
9 years ago
Hi all,
Work Completed = 80% = 80/100 = 4/5.
So, Remaining = 1- 4/5 = 1/5.
A + B complete this in 3 days so if they had continued total time required will be 5 * 3 = 15 days.
A individual complete it in 5/4 * 20 = 25 Days.
Then, B individual 1 day Work = 1/(A + B) - 1/A = 1/15 - 1/25 = 2/75.
So, B will complete whole work in 75/2 = 37 1/2.
Work Completed = 80% = 80/100 = 4/5.
So, Remaining = 1- 4/5 = 1/5.
A + B complete this in 3 days so if they had continued total time required will be 5 * 3 = 15 days.
A individual complete it in 5/4 * 20 = 25 Days.
Then, B individual 1 day Work = 1/(A + B) - 1/A = 1/15 - 1/25 = 2/75.
So, B will complete whole work in 75/2 = 37 1/2.
Yash said:
7 years ago
We can solve it like this way also;
A do 80% of work in 20 days.
So,
A's one day's work = 80/100 * 1/20.
= 1/25.
Now A and B do remaining work in 3 days.
so we find remaining work and i.e. (1-1/25) = 24/25.
Now we multiply 24/25 by because of they(A and B) complete it in 3 days = 72/25 and the answer is 37 1/2.
A do 80% of work in 20 days.
So,
A's one day's work = 80/100 * 1/20.
= 1/25.
Now A and B do remaining work in 3 days.
so we find remaining work and i.e. (1-1/25) = 24/25.
Now we multiply 24/25 by because of they(A and B) complete it in 3 days = 72/25 and the answer is 37 1/2.
Likhitha said:
9 years ago
A does 80% of work in 20 days.
Then A can do 100% of work in 25 days and 20% of work in 5 days.
A + B together finish the remaining 20% of work in 3 days.
For 20% of work B alone:
3/5 + 3/x = 1.
x = 7.5 days.
For 20% of work B alone takes 7.5 days then for 100% of work B takes,
20% = 7.5.
100% = ?.
100 * 7.5/20 = 37.5 = 37 1/2.
Then A can do 100% of work in 25 days and 20% of work in 5 days.
A + B together finish the remaining 20% of work in 3 days.
For 20% of work B alone:
3/5 + 3/x = 1.
x = 7.5 days.
For 20% of work B alone takes 7.5 days then for 100% of work B takes,
20% = 7.5.
100% = ?.
100 * 7.5/20 = 37.5 = 37 1/2.
Vaibhav said:
1 decade ago
In 20 days A does 80% work. So in one day =80/20=4%
Let we start from sunday then S M T W T F S....4% each day then total 25 days will be taken by A to 100% work done .
Similarly for A+B, in 3 days (100-80)=20% work done. for one day=20/3%..so for 100% counting on each day 15 days will come
So a+b=1/15=>b=1/15-1/20=>2/75
Let we start from sunday then S M T W T F S....4% each day then total 25 days will be taken by A to 100% work done .
Similarly for A+B, in 3 days (100-80)=20% work done. for one day=20/3%..so for 100% counting on each day 15 days will come
So a+b=1/15=>b=1/15-1/20=>2/75
Bipinvvijayan@gmail.com said:
1 decade ago
Let us say that the work is of 100 units then A finishes 80 units in 20 days which means 80/20 = 4 units per day.
Remaining work = 20 units.
Units finished per day = 4 + B.
Days taken = 3 = 20/(4 + B) = 12 + 3B = 20.
3B = 8.
B = 8/3.
If B finishes 8/3 units every day then to finish 100 units B will take 100 x 3/8 = 37.5 days.
Remaining work = 20 units.
Units finished per day = 4 + B.
Days taken = 3 = 20/(4 + B) = 12 + 3B = 20.
3B = 8.
B = 8/3.
If B finishes 8/3 units every day then to finish 100 units B will take 100 x 3/8 = 37.5 days.
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