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:
166 comments Page 4 of 17.
Jay said:
2 decades ago
@shefali..the 15 days is nothing but remaining work probability. 4/5 i.e 80% work is done by A so remaining is 1-(4/5)= 1/5. its same like p+q=1 in probability.
n same like 3*5=15 days
n same like 3*5=15 days
(1)
Balaji said:
2 decades ago
Thank you very much rajendra.
(1)
Shanmug said:
2 decades ago
@Baskar you have done great job. Just carry on.
(1)
Pratswinz said:
2 decades ago
@Bhaskar your explanation was superb. Carry on dude.
(1)
Mathi said:
1 decade ago
A = (1/20) * (80/100) = 1/25
1/A + 1/B =1/3(20/100)
1/B=(1/15) - (1/25) =2/75
1/A + 1/B =1/3(20/100)
1/B=(1/15) - (1/25) =2/75
(1)
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)
Namrata Gujar said:
5 years ago
A=80%
Remain 100 - 80 = 20%.
A = (1/20) * (80/100) = 1/25.
A+b = (1/3)+(20/100) = 1/15.
A+b.
(1/25) + b = 1/15.
B = 2/75,
B = 75/2,
B = 37(1/2).
Remain 100 - 80 = 20%.
A = (1/20) * (80/100) = 1/25.
A+b = (1/3)+(20/100) = 1/15.
A+b.
(1/25) + b = 1/15.
B = 2/75,
B = 75/2,
B = 37(1/2).
(1)
Narayanan said:
2 months ago
A completes 80% of the work in 20 days, which means 80/100=4/5 unit of work are already completed by A.
therefore, remaining work = 1 - 4/5 = 1/5 units is remaining work,
1/5 work is completed by A + B.
Converting fractions into 1 unit of work.
Formula = total days taken by A to finish work x reciprocal of finished work.
So, A = 20 x 5/4 = 25 days.
A+B = 3 x 5/1 = 15 days.
By substituting A in A+B, we get 75/2, which can be written as 37 1/2.
therefore, remaining work = 1 - 4/5 = 1/5 units is remaining work,
1/5 work is completed by A + B.
Converting fractions into 1 unit of work.
Formula = total days taken by A to finish work x reciprocal of finished work.
So, A = 20 x 5/4 = 25 days.
A+B = 3 x 5/1 = 15 days.
By substituting A in A+B, we get 75/2, which can be written as 37 1/2.
(1)
Snehagoud said:
2 decades ago
A did only 80% of work out of total work in 20 days so
work done by A=80/100=5/4
so total workdone by A=20*5/4
work done by A=80/100=5/4
so total workdone by A=20*5/4
Shefali said:
2 decades ago
How do we get that A & B together can do work in 15 days?
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