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 8 of 17.
RAjesh Kumar said:
6 years ago
80% = 4/5.
A does 4/5 work in 20 days.
A 1 day work =(4/5)/20 = 1/25,
remaining work = 1/5.
A + B does 1/5 work in 3 days.
A + B 1 day work=(1/5)/3 = 1/15.
Therefore;
B's 1 day work = (a+b)-a = 1/15-1/25 = 2/75.
A does 4/5 work in 20 days.
A 1 day work =(4/5)/20 = 1/25,
remaining work = 1/5.
A + B does 1/5 work in 3 days.
A + B 1 day work=(1/5)/3 = 1/15.
Therefore;
B's 1 day work = (a+b)-a = 1/15-1/25 = 2/75.
Sonam said:
1 decade 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.
Punitsw said:
10 years ago
In simple words:
A completes 80% in 20 days so would 92% in 23 days.
Remaining 8% completed by B in 3 days (21 - 23rd).
Now if B completes 8% in 3 days. So will be able to complete 100% in 37.5 days (3 x 100/8).
A completes 80% in 20 days so would 92% in 23 days.
Remaining 8% completed by B in 3 days (21 - 23rd).
Now if B completes 8% in 3 days. So will be able to complete 100% in 37.5 days (3 x 100/8).
Mayur said:
7 years ago
80% work --> 20 Days, Then
100% work --> ?? Days.
i.e 20 * 100/80 = 25.
Similarly (remaining work) = 20% work done in 3 days that means 100% work done in 15 Days.
Now
1/25+B = 1/15,
1/15-1/25 = B,
2/75,
37.5.
100% work --> ?? Days.
i.e 20 * 100/80 = 25.
Similarly (remaining work) = 20% work done in 3 days that means 100% work done in 15 Days.
Now
1/25+B = 1/15,
1/15-1/25 = B,
2/75,
37.5.
Mayuri said:
1 decade ago
A's 1 day work = 1/20*80/100.
= 1/25.
A+B 1 day work = 1/3*20/100.
= 1/15.
A+B-A=B'S 1 day work = 1/25-1/15.
= 1/75.
= 37 1/2.
Simple.
= 1/25.
A+B 1 day work = 1/3*20/100.
= 1/15.
A+B-A=B'S 1 day work = 1/25-1/15.
= 1/75.
= 37 1/2.
Simple.
Jay said:
1 decade 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)
Thamaraiselvam said:
1 decade ago
A : 80%
80%\20days = 4%(A's one day work).
And remaining work 20% =3 days(A(4% one day work)+B).
12+B=20
B=8% for 3 days.
80% for 30 days.
96 % for 36 days.
100 for 37 1/2 days :-).
80%\20days = 4%(A's one day work).
And remaining work 20% =3 days(A(4% one day work)+B).
12+B=20
B=8% for 3 days.
80% for 30 days.
96 % for 36 days.
100 for 37 1/2 days :-).
Krishnaveni said:
2 years ago
80%--->20days.
20%--->'x' days.
x = [20 * 20%]/80%.
x = 5 days.
1/5 + 1/y = 1/3.
1/y = 2/15.
20%--->15/2 days.
100%--->'z' days.
z = [(15/2) * 100%]/20%.
z = 75/2 days.
20%--->'x' days.
x = [20 * 20%]/80%.
x = 5 days.
1/5 + 1/y = 1/3.
1/y = 2/15.
20%--->15/2 days.
100%--->'z' days.
z = [(15/2) * 100%]/20%.
z = 75/2 days.
(30)
Manjunath Deepak said:
8 years ago
@Swapraj.
This is how it goes,
A---> 80% work--->20 days.
100% work---> How many days (say 'X' days).
Then you cross multiply it and you get the solution.
This is how it goes,
A---> 80% work--->20 days.
100% work---> How many days (say 'X' days).
Then you cross multiply it and you get the solution.
Aliya said:
9 months ago
A's work rate = 80% in 20.days =80%/20=4
Remaining work of A and B = 100%-80%= 20% in 3 days = 20%/3.
B can do work = 20/3 - 4 = 20-12/3 = 8/3%.
B 100% work = 100/8/3 = 37.5 days.
Remaining work of A and B = 100%-80%= 20% in 3 days = 20%/3.
B can do work = 20/3 - 4 = 20-12/3 = 8/3%.
B 100% work = 100/8/3 = 37.5 days.
(32)
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