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 3 of 17.
Abhijeet said:
4 years ago
A can do 80% of work in 20 Days.
So, 20 days = 80%,
1 day = ?
= 4%,
A and B worked for 3 days so 4% A can do in 1 day and in 3 days it is 3*4=12%.
A and B together worked and completed the remaining 20% of the work in 3 days which A work is 12%.
So, A+B =20%,
12% +B =20,
B = 8%,
B worked 8% in 3 days,
3 days = 8%,
1 day = ?
=2.66%.
The whole work is 100% in itself,
B 100/2.66 ==37.5 or 37 1/2.
So, 20 days = 80%,
1 day = ?
= 4%,
A and B worked for 3 days so 4% A can do in 1 day and in 3 days it is 3*4=12%.
A and B together worked and completed the remaining 20% of the work in 3 days which A work is 12%.
So, A+B =20%,
12% +B =20,
B = 8%,
B worked 8% in 3 days,
3 days = 8%,
1 day = ?
=2.66%.
The whole work is 100% in itself,
B 100/2.66 ==37.5 or 37 1/2.
(147)
Chandu said:
1 decade ago
80% = 20 days.
100% = 20x100/80 = 25 days.
i.e. A alone can do whole work in 25days, A's one day work = 1/25.
But A worked 20 days (it mean 20/25 work completed)remaining 5/25.
A+B worked for 3 days to complete the remaining 5/25 part of work.
A's 3 days work = 1/25+ 1/25+ 1/25 = 3/25.
Remaining 2/25 part of work is done by B in 3 days.
3 days----2/25.
1 day-----?.
1 day----2/(25*3) = 2/75.
Total work done by B is 75/2 = 37 1/2.
100% = 20x100/80 = 25 days.
i.e. A alone can do whole work in 25days, A's one day work = 1/25.
But A worked 20 days (it mean 20/25 work completed)remaining 5/25.
A+B worked for 3 days to complete the remaining 5/25 part of work.
A's 3 days work = 1/25+ 1/25+ 1/25 = 3/25.
Remaining 2/25 part of work is done by B in 3 days.
3 days----2/25.
1 day-----?.
1 day----2/(25*3) = 2/75.
Total work done by B is 75/2 = 37 1/2.
Thirumalai Murugan said:
2 years ago
(no of days required A to complete 100% work + no of days required B to complete 100% work) * no of days
= no of days required complete whole work by A+B -----> 1
A per-day work = 20/80 = 1/ 4 meaning 4 units/day.
Hence, no of days required A to complete 100% work = 100/4 = 25 days.
No of days are required to complete the whole work by A+B = 100/20 = 5.
The sub in 1.
(1/25 +1/B) *3 = 1/5.
3/B = 2/25.
B = 25*3/2
B = 37.5
= no of days required complete whole work by A+B -----> 1
A per-day work = 20/80 = 1/ 4 meaning 4 units/day.
Hence, no of days required A to complete 100% work = 100/4 = 25 days.
No of days are required to complete the whole work by A+B = 100/20 = 5.
The sub in 1.
(1/25 +1/B) *3 = 1/5.
3/B = 2/25.
B = 25*3/2
B = 37.5
(8)
Kasi Viswesh said:
2 years ago
This can also be solved in this way.
A - 80% work in 20 days .
=>1/A=1/20 (1 day work of A) ---> 1
Also Given remaining 20% work done in 3 days by help of B.
Let us calculate days if they work for other 80%.
20% = 3 days.
80% = x.
x = 12 days.
=> 1/A + 1/B = 1/12.
Substitute value of 1/A from eq 1
then B = 30
=> 80% = 30 days,
100% = x.
By calculating x = 37.5.
So, B alone can finish work in 37.5 days.
A - 80% work in 20 days .
=>1/A=1/20 (1 day work of A) ---> 1
Also Given remaining 20% work done in 3 days by help of B.
Let us calculate days if they work for other 80%.
20% = 3 days.
80% = x.
x = 12 days.
=> 1/A + 1/B = 1/12.
Substitute value of 1/A from eq 1
then B = 30
=> 80% = 30 days,
100% = x.
By calculating x = 37.5.
So, B alone can finish work in 37.5 days.
(3)
Ammus said:
1 decade ago
80% of work will be completed int 20days. ie) 80/100 = 4/5.
Remaining 20% of work ie, 20/100 = 1/5.
A can do 100 % of work in 25 days,
So A's per day work is 1/25.
Now A+B together do the 20% of work.
(A + B) work = 3 days.
1/5 work = 3 work days.
1 work = 5 * 3 days,
Work = 15 days.
(A+B) per day work is = 1/15,
A's per day work is 1/25,
Now A + B = 1/15,
1/25 + B = 1/15,
B = 1/15 - 1/25,
B alone = 75/2 ie. 37 1/2 days.
Remaining 20% of work ie, 20/100 = 1/5.
A can do 100 % of work in 25 days,
So A's per day work is 1/25.
Now A+B together do the 20% of work.
(A + B) work = 3 days.
1/5 work = 3 work days.
1 work = 5 * 3 days,
Work = 15 days.
(A+B) per day work is = 1/15,
A's per day work is 1/25,
Now A + B = 1/15,
1/25 + B = 1/15,
B = 1/15 - 1/25,
B alone = 75/2 ie. 37 1/2 days.
Wilson said:
10 years ago
A's 1 day work = 80% / 20 days
= 80/20
= 4 ( 4% work per day done by 'A' )
Remaining, (100 - 80) 20% work done by 'A' and 'B' in 3 days.
It means 'A' must have done 4% work per day, So, in 3 Days = 4% * 3.
= 4 * 3.
= 12.(12%work done by 'A' out of 20%).
Now, 8% (20-12) work done by 'B' in 3 Days.
Therefore, 'B' Alone can do Work = 100/8 * 3.
= 37 1/2 days.
= 80/20
= 4 ( 4% work per day done by 'A' )
Remaining, (100 - 80) 20% work done by 'A' and 'B' in 3 days.
It means 'A' must have done 4% work per day, So, in 3 Days = 4% * 3.
= 4 * 3.
= 12.(12%work done by 'A' out of 20%).
Now, 8% (20-12) work done by 'B' in 3 Days.
Therefore, 'B' Alone can do Work = 100/8 * 3.
= 37 1/2 days.
$ha$ha said:
1 decade ago
Let total work=100%.
A do 80% work = 20 days.
A's 1 day work= 1/20 * 80% i:e 1/20 * 80/100 = 2/50.
Now,Remaining work is 100-80=20%.
So, A and B together complete remaining work i.e 20% in 3days.
Therefore A and B 1 day work = 1/3 * 20% i:e 1/3 * 20/100= 1/15.
Now, B's alone 1 day work is,
A+B=1/15
2/50+B=1/15
B=1/15 - 2/50 = 10-6/150 = 2/75.
Now, B alone can complete work in 75/2 days i.e option C.
A do 80% work = 20 days.
A's 1 day work= 1/20 * 80% i:e 1/20 * 80/100 = 2/50.
Now,Remaining work is 100-80=20%.
So, A and B together complete remaining work i.e 20% in 3days.
Therefore A and B 1 day work = 1/3 * 20% i:e 1/3 * 20/100= 1/15.
Now, B's alone 1 day work is,
A+B=1/15
2/50+B=1/15
B=1/15 - 2/50 = 10-6/150 = 2/75.
Now, B alone can complete work in 75/2 days i.e option C.
Riyaz said:
1 decade ago
A does 80% of work in 20 days which means he does 4% of work in a day (80/20 =4).
A and b does the remaining 20% work in 3 days which means in this 20 % of work A's contribution will be 4*3=12%.
Work done by b in 3 days = 20-12 = 8%.
Work done by b in 1 day = 8/3= 2.66.
Time taken by B to complete whole work= 100/2.66= 37.59.
We can't get exact answer but this will be time consuming.
A and b does the remaining 20% work in 3 days which means in this 20 % of work A's contribution will be 4*3=12%.
Work done by b in 3 days = 20-12 = 8%.
Work done by b in 1 day = 8/3= 2.66.
Time taken by B to complete whole work= 100/2.66= 37.59.
We can't get exact answer but this will be time consuming.
(1)
Rahul said:
1 decade ago
Hi, one easy and time-saving method is:
A done 80% work in 20 days.
So, one day work of A is = 80/20 = 4%.
Here, remaining work is = 100 - 80.
=20%.
A and B both together remaining work and they take 3 days to accomplish it.
During this three day, A's work is = 4% * 3 = 12%.
Then, B's work during 3 days = 8%.
Work - Days.
8% - 3.
100% - (?).
100 * 3/8 = 300/8 = 37.5 days.
A done 80% work in 20 days.
So, one day work of A is = 80/20 = 4%.
Here, remaining work is = 100 - 80.
=20%.
A and B both together remaining work and they take 3 days to accomplish it.
During this three day, A's work is = 4% * 3 = 12%.
Then, B's work during 3 days = 8%.
Work - Days.
8% - 3.
100% - (?).
100 * 3/8 = 300/8 = 37.5 days.
Taraka Siva Sai Ponnuru said:
2 years ago
Given
A completes 80% work in 20 days (20% work in 5 days).
A alone can complete 100% work in 25days(20/80*100=25)
A+B together complete 20% of the work in 3 days
A+B together complete 100% of the work in 15 days.
Here we need to consider only 100% work done by A+B&A.
(A+B)-A = [1/15 - 1/25].
LCM of 15, 25 is 75.
(A+B)-A = [5-3]/75,
(A+B)-A = 2/75,
(A+B)-A = 37.5.
A completes 80% work in 20 days (20% work in 5 days).
A alone can complete 100% work in 25days(20/80*100=25)
A+B together complete 20% of the work in 3 days
A+B together complete 100% of the work in 15 days.
Here we need to consider only 100% work done by A+B&A.
(A+B)-A = [1/15 - 1/25].
LCM of 15, 25 is 75.
(A+B)-A = [5-3]/75,
(A+B)-A = 2/75,
(A+B)-A = 37.5.
(23)
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