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 2 of 17.
Ramya reddy said:
2 years ago
80% of the work in 20 days means 4/5.
100% he will complete in 25 days.
Now, the remaining 20% of the work in 3days means;
1-4/5 = 1/5 this is for one day
For 3days 3*1/5 = 1/15,
Now [1/15 - 1/25] = 2/75.
Rev= 75/2=37.5
100% he will complete in 25 days.
Now, the remaining 20% of the work in 3days means;
1-4/5 = 1/5 this is for one day
For 3days 3*1/5 = 1/15,
Now [1/15 - 1/25] = 2/75.
Rev= 75/2=37.5
(14)
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)
Keerthan G said:
2 years ago
A= 80% in 20 days.
100% in 25 days.
A + B = 20% in 3 days.
100% in 15 days.
LCM OF 15 and 25 is 75.
Efficiency of A is 75/25 = 3.
Efficiency of A+B is 75/15 = 5.
A+B = efficiency of A+B is 5 so that,
A+B = 5,
3+B = 5,
B = 2.
THEN 75 IS TOTAL WORKS.
So, 75/2 = 37.5.
100% in 25 days.
A + B = 20% in 3 days.
100% in 15 days.
LCM OF 15 and 25 is 75.
Efficiency of A is 75/25 = 3.
Efficiency of A+B is 75/15 = 5.
A+B = efficiency of A+B is 5 so that,
A+B = 5,
3+B = 5,
B = 2.
THEN 75 IS TOTAL WORKS.
So, 75/2 = 37.5.
(78)
Rak said:
2 years ago
Thanks @Karan.
(5)
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)
Jeevesh said:
2 years ago
@Rajendra.
Thank you for explaining.
Thank you for explaining.
(4)
Karan said:
3 years ago
A = 80% in 20 days.
80% = 80/100 = 4/5.
A = 4% Daily work.
80-100 = 20% of work remaining.
20% of work done by A+B in 3 days.
A = 4% Daily work in 3 days.
A = 4×3=12%.
20 - 12 = 8%.
B = 8%.
B = 8/100%×3 = 37.5 = 37 1/2.
80% = 80/100 = 4/5.
A = 4% Daily work.
80-100 = 20% of work remaining.
20% of work done by A+B in 3 days.
A = 4% Daily work in 3 days.
A = 4×3=12%.
20 - 12 = 8%.
B = 8%.
B = 8/100%×3 = 37.5 = 37 1/2.
(96)
Joy khwaka said:
3 years ago
Finally, I understood the concept, Thanks @Rajendra.
(4)
Keshav T said:
3 years ago
A = 20/(80/100)=20/(4/5)
A = 20*5/4.
A = 25 days i.e 1/25 days.
1-(4/5 )work is done = 1/5.
A+B = 1/15.
1/15 - 1/25 = 2/75.
75/2 i e 37(1/2) days.
A = 20*5/4.
A = 25 days i.e 1/25 days.
1-(4/5 )work is done = 1/5.
A+B = 1/15.
1/15 - 1/25 = 2/75.
75/2 i e 37(1/2) days.
(21)
Abhijeet said:
3 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.
(145)
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