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 5 of 17.
SUJALA said:
10 years ago
A is doing 80% work in 20 days.
80/100 = 20.
4/5 = 20/1 (cross multiplication).
= 25 days.
It means a can take time to complete 100% of work for 25 days.
A+B is doing 20% of work in 3 days.
= 20/100 = 3/1 (cross multiplication) = 15 days.
Now B to get complete 100% of work is?
(A+B)-A = B.
= 1/15-1/25 = 2/75 = 37*1/2.
80/100 = 20.
4/5 = 20/1 (cross multiplication).
= 25 days.
It means a can take time to complete 100% of work for 25 days.
A+B is doing 20% of work in 3 days.
= 20/100 = 3/1 (cross multiplication) = 15 days.
Now B to get complete 100% of work is?
(A+B)-A = B.
= 1/15-1/25 = 2/75 = 37*1/2.
Imtiyaz said:
8 months ago
A can do 80% of work in 20 days.
A + B 20% of work in 3 days.
A alone can do 20% of work in 5 days and A+B can do 80% in 12 days.
Now, A 100% in 25 days and A + B in 15 days.
L.C.M of 15 and 25 = 75
The efficiency of A is 3/day and of A + B 5/day.
If A efficiency is 3, then B is 2.
B days = work/B efficiency.
=> 75/2 = 37.5.
A + B 20% of work in 3 days.
A alone can do 20% of work in 5 days and A+B can do 80% in 12 days.
Now, A 100% in 25 days and A + B in 15 days.
L.C.M of 15 and 25 = 75
The efficiency of A is 3/day and of A + B 5/day.
If A efficiency is 3, then B is 2.
B days = work/B efficiency.
=> 75/2 = 37.5.
(8)
Mini said:
1 decade ago
Easy Method:-
A does 80% work in 20 days= 80%/20=80/100*1/20 =1/25...(i)
A and B togheter finish the remaining work(which is 20%) in 3 days.
so (A+B) do 20% work in 3days= 20%/3=20/100*1/3 =1/15....(ii)
Now we hv to find B's Work days
So subtract equ. (ii) from (i)
(A+B)-A =1/15-1/25
B =2/75
B =37 1/2 DAYS
A does 80% work in 20 days= 80%/20=80/100*1/20 =1/25...(i)
A and B togheter finish the remaining work(which is 20%) in 3 days.
so (A+B) do 20% work in 3days= 20%/3=20/100*1/3 =1/15....(ii)
Now we hv to find B's Work days
So subtract equ. (ii) from (i)
(A+B)-A =1/15-1/25
B =2/75
B =37 1/2 DAYS
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 :)
Keerthu said:
11 months ago
A in 80% work done 20 days.
A in 100% work done 100*20/80= 25 days.
A+B in 20% work done 3 days.
A+B in 100% work done 100*3/20= 15 days.
A = 25 days.
A+B = 15 days.
LCM OF 75.
1 DAY OF WORK 75/25 = 3
1 DAY A+B WORK 75/15 = 5.
A + B = 5
3 + B = 5
B = 2
B total working days =>75/2 = 37.5 days.
A in 100% work done 100*20/80= 25 days.
A+B in 20% work done 3 days.
A+B in 100% work done 100*3/20= 15 days.
A = 25 days.
A+B = 15 days.
LCM OF 75.
1 DAY OF WORK 75/25 = 3
1 DAY A+B WORK 75/15 = 5.
A + B = 5
3 + B = 5
B = 2
B total working days =>75/2 = 37.5 days.
(51)
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.
Harish said:
6 years ago
80% is completed so remaining is 20% work.
This 20% work is completed by A&B together in 3 days,
If 20% is 3 days then 100% is 15 days,
A completed 80% in 20days then A can complete 100% in 25 days,
So B's work =1/15 -1/25 =2/75,
2 work in 75 days,
1 work in 75/2 days,
= 37 1/2 days.
This 20% work is completed by A&B together in 3 days,
If 20% is 3 days then 100% is 15 days,
A completed 80% in 20days then A can complete 100% in 25 days,
So B's work =1/15 -1/25 =2/75,
2 work in 75 days,
1 work in 75/2 days,
= 37 1/2 days.
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.
(77)
Deepa said:
3 years ago
A:
80% in 20 days then
100% in x days
Cross multiply them you will get 25days
A+B:
20% in 3 days then
100% in y days
Cross multiply them you will get y=15.
Now: A's one day work is 1/25.
& A+B's one-day work is 1/15.
A+B one day work minus A one day work =1/15 - 1/25 = 75/2.
80% in 20 days then
100% in x days
Cross multiply them you will get 25days
A+B:
20% in 3 days then
100% in y days
Cross multiply them you will get y=15.
Now: A's one day work is 1/25.
& A+B's one-day work is 1/15.
A+B one day work minus A one day work =1/15 - 1/25 = 75/2.
(16)
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.
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