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 4 of 17.
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)
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.
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.
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.
Balaji said:
1 decade ago
I can't understand the simple step anyone friends tell me (1/15-1/25) please tell me?
Seema duhan said:
1 decade ago
A = (1/20)*(80%) = (1/20)*(80/100) = 1/25. (EQUATION 1).
Remaining work=100%-80%=20%.
A+B=(1/3)*(20%)=(1/3)*(20/100)=1/15. (EQUATION 2).
Put equation 1 in equation 2, we get:
(1/25)+B = 1/15.
B = 2/75.
So B alone can do this work in 75/2 days.
Remaining work=100%-80%=20%.
A+B=(1/3)*(20%)=(1/3)*(20/100)=1/15. (EQUATION 2).
Put equation 1 in equation 2, we get:
(1/25)+B = 1/15.
B = 2/75.
So B alone can do this work in 75/2 days.
Shivaram goud said:
1 decade ago
@Snehagoud.
Can you check the what is 80/100 = 5/4?
Can you check the what is 80/100 = 5/4?
Ravi parashar said:
1 decade ago
Short Cut. This method you can do orally.
A is able to save two days which means that this is the work done by B actually in 3 days. Which turns out to be.
A 2 days work = 8 which is equal to 3 days work of B.
B in 3 days does 8 unit of work.
B in 100 days will do (3/8) *100 = Option C.
A is able to save two days which means that this is the work done by B actually in 3 days. Which turns out to be.
A 2 days work = 8 which is equal to 3 days work of B.
B in 3 days does 8 unit of work.
B in 100 days will do (3/8) *100 = Option C.
Sravya said:
1 decade ago
80% ------ 20 days.
100% ----- ?.
(20/80)*100 = 25 days.
A can complete 100% work in 25 days.
Remaining (120% work (A&B))similarly,
20%----- 3 days.
100%----- ? we get 15 days(1/15 work per day).
we know that A+B = 1/15.
B = 1/15 - 1/25 : Option C.
100% ----- ?.
(20/80)*100 = 25 days.
A can complete 100% work in 25 days.
Remaining (120% work (A&B))similarly,
20%----- 3 days.
100%----- ? we get 15 days(1/15 work per day).
we know that A+B = 1/15.
B = 1/15 - 1/25 : Option C.
VIKRAM SIHAG said:
1 decade ago
Efficeny of A+B = 20/3 = 6.66.
EFFICENCY OF A = 80/20 = 4.00.
THEN EFFICENCY OF B = 6.66-4.00 = 2.66.
DAYS TAKEN BY B = 100/2.66 = 37.5.
EFFICENCY OF A = 80/20 = 4.00.
THEN EFFICENCY OF B = 6.66-4.00 = 2.66.
DAYS TAKEN BY B = 100/2.66 = 37.5.
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