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 14 of 17.
Ram@Sravs said:
1 decade ago
Hi. @Supreeth:
In St-4:
Why had you reversed the 2/25 part to 25/2 and multiplied with 3?
Can you Explain please.
In St-4:
Why had you reversed the 2/25 part to 25/2 and multiplied with 3?
Can you Explain please.
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.
Supreeth said:
1 decade ago
St-1:
80%=20.
.'.(100*20)/80 = 25 days.
100%=?
St-2:
For 23 days A would have completed 23/25 part of the work,
St-3:
(25/25)-(23/25) = 2/25 part of work is completed by B in 3 days.
St-4:
.'. in 1 day (25/2)*3 = 37 1/2.
80%=20.
.'.(100*20)/80 = 25 days.
100%=?
St-2:
For 23 days A would have completed 23/25 part of the work,
St-3:
(25/25)-(23/25) = 2/25 part of work is completed by B in 3 days.
St-4:
.'. in 1 day (25/2)*3 = 37 1/2.
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)
Ajith said:
1 decade ago
1) 100*20/80 =25.
2) Total work done in 25 days.
3) Remaining work finished in 5 days.
4) If A&B work together 3*5=15.
5) A's one days work 1/25.
6) A+B one days work 1/15.
7) 1/15 - 1/25 = 4/150= 2/75.
8) So B alone would do the work in 75/2= 37 1/2.
2) Total work done in 25 days.
3) Remaining work finished in 5 days.
4) If A&B work together 3*5=15.
5) A's one days work 1/25.
6) A+B one days work 1/15.
7) 1/15 - 1/25 = 4/150= 2/75.
8) So B alone would do the work in 75/2= 37 1/2.
Yogesh said:
1 decade ago
My method:
A's 1% work done time = 80/20 = 4%.
Means in 1 day a completes 4%......(1).
Now,
A+B 1 day work = 20/3.
B work = 20/3 - 4/1 = 8/3.
B work in 1 day = 8/3 ---- (2).
So now,
For 100% work by B is:
8/3*1/100 = 300/8 = 37.5 days. work
Answer..(:
A's 1% work done time = 80/20 = 4%.
Means in 1 day a completes 4%......(1).
Now,
A+B 1 day work = 20/3.
B work = 20/3 - 4/1 = 8/3.
B work in 1 day = 8/3 ---- (2).
So now,
For 100% work by B is:
8/3*1/100 = 300/8 = 37.5 days. work
Answer..(:
$ha$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.
Alle chandra shekar said:
1 decade ago
Please tell me short cut method.
Chandana said:
1 decade ago
80/100 = 4/5.
5/4*20 = 25days.
A and B completes the remaining work in 3 days i.e.,
3*5 = 15days.
A's 1 days work is 1/25.
B's 1 days work is 1/15.
Therefore, b's one days work will be,
1/5-1/25 = 5-3 / 75 = 2/75 i.e 75/2 will give us 37.5, So B alone will complete the entire work in 37.5 OR 37 1/2 :)
5/4*20 = 25days.
A and B completes the remaining work in 3 days i.e.,
3*5 = 15days.
A's 1 days work is 1/25.
B's 1 days work is 1/15.
Therefore, b's one days work will be,
1/5-1/25 = 5-3 / 75 = 2/75 i.e 75/2 will give us 37.5, So B alone will complete the entire work in 37.5 OR 37 1/2 :)
Suganya said:
1 decade ago
Simple method:.
A's one day work 80/20=4%.
A's three days work 12%.
The remaining work is only done by B in that three days=20%-12%=8%.
B's one days work=8/3%.
B completes 100% work in.
8/3% * x =100%.
So x=75/2=37.5.
A's one day work 80/20=4%.
A's three days work 12%.
The remaining work is only done by B in that three days=20%-12%=8%.
B's one days work=8/3%.
B completes 100% work in.
8/3% * x =100%.
So x=75/2=37.5.
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