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 3 of 17.
Kasi Viswesh said:
1 year 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:
9 years 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:
9 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:
9 years 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:
10 months 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.
(16)
Pooja Gowda said:
9 years ago
The total work is 100 unit.
A can do 80 unit in 20 days. So he can do 4 unit in 1 days.
Now A has finished 80 units so remaining work is 20 unit.
So, 20 unit work takes 3 days time to complete in which A will do 12 unit.
(since A do 4 unit/days).
Thus, B do 8 unit in 3 days.
And total work is 100 unit so B will take (3/8) * 100 = 37.5 days to complete total work.
A can do 80 unit in 20 days. So he can do 4 unit in 1 days.
Now A has finished 80 units so remaining work is 20 unit.
So, 20 unit work takes 3 days time to complete in which A will do 12 unit.
(since A do 4 unit/days).
Thus, B do 8 unit in 3 days.
And total work is 100 unit so B will take (3/8) * 100 = 37.5 days to complete total work.
Raj said:
3 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 the 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 the 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.
(14)
Vaibhav Shinde said:
12 months ago
A -> 80% work in 20 days.
A + B ---> 20% work in 3 days.
A --> 100% work in 25 days.
A+B ->100%work in 15 days
LCM of 25 and 15 is 75.
Capacity of A is -->3 units
Capacity of A+B ---> 5 units.
So, the total work was 75(LCM).
B capacity = A+B (Capacity)-A(capacity).
B(Capacity) = 5-3.
B(Capacity) = 2.
B(work) = totalWork/B(Capacity).
B(Work) = 75/2.
B(Work) = 37.5.
A + B ---> 20% work in 3 days.
A --> 100% work in 25 days.
A+B ->100%work in 15 days
LCM of 25 and 15 is 75.
Capacity of A is -->3 units
Capacity of A+B ---> 5 units.
So, the total work was 75(LCM).
B capacity = A+B (Capacity)-A(capacity).
B(Capacity) = 5-3.
B(Capacity) = 2.
B(work) = totalWork/B(Capacity).
B(Work) = 75/2.
B(Work) = 37.5.
(8)
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers