Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 1)
1.
A can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the fraction of the work that is left is :
Answer: Option
Explanation:
| A's 1 day's work = | 1 | ; |
| 15 |
| B's 1 day's work = | 1 | ; |
| 20 |
| (A + B)'s 1 day's work = |  |
1 | + | 1 |  |
= | 7 | . |
| 15 | 20 | 60 |
| (A + B)'s 4 day's work = | |
7 | x 4 | |
= | 7 | . |
| 60 | 15 |
| Therefore, Remaining work = | |
1 - | 7 | |
= | 8 | . |
| 15 | 15 |
Discussion:
351 comments Page 7 of 36.
Beer ibrahim said:
2 decades ago
Why (1-7/15) is applied ?
(1)
Sundar said:
2 decades ago
@Beer Ibrahim
Q: Why (1-7/15) is applied ?
Ans: To calculate the work remaining. Work remaining = 8/15.
Note: From the above answer, we can say 15/8 days required to
complete the remaining work by A and B.
Hope this will help you. Have nice day!
Q: Why (1-7/15) is applied ?
Ans: To calculate the work remaining. Work remaining = 8/15.
Note: From the above answer, we can say 15/8 days required to
complete the remaining work by A and B.
Hope this will help you. Have nice day!
(1)
PRAKASH said:
2 decades ago
For A:-
15 days for 1 job
in 1 day 1/15 (part of the one job)
for B:-
20 days for 1 job
in 1 day 1/20 (part of the one job)
FOR BOTH IN ONE DAY:-
1/15+1/20=7/60
FOR BOTH IN 4 DAYS:-
(7/60)*4=7/15(THEY HAVE DONE)
THE REST PART OF THE JOB IS:-
1-(7/15)=8/15 (ANS)
15 days for 1 job
in 1 day 1/15 (part of the one job)
for B:-
20 days for 1 job
in 1 day 1/20 (part of the one job)
FOR BOTH IN ONE DAY:-
1/15+1/20=7/60
FOR BOTH IN 4 DAYS:-
(7/60)*4=7/15(THEY HAVE DONE)
THE REST PART OF THE JOB IS:-
1-(7/15)=8/15 (ANS)
(1)
Swetha said:
1 decade ago
We can solve this problem by another way also..let us see..
A can do a work in 15 days
B can do a work in 20 days
Take LCM for 15 & 20 i.e Total work = 60
Then,
A's capacity = 60/15 = 4
B's capacity = 60/20 = 3
They work together for 4 days,
Then, A's capacity + B's capacity = 4 + 3 =7
AB's one day capacity = 7
since they work for 4 days, they have done 4x7 =28 work
Work left = Total work - work done by AB
= 60 - 28 = 32
Remaining work / total work = 32 / 60 = 8 / 15
This method will take less time to compute guys...please try it.
A can do a work in 15 days
B can do a work in 20 days
Take LCM for 15 & 20 i.e Total work = 60
Then,
A's capacity = 60/15 = 4
B's capacity = 60/20 = 3
They work together for 4 days,
Then, A's capacity + B's capacity = 4 + 3 =7
AB's one day capacity = 7
since they work for 4 days, they have done 4x7 =28 work
Work left = Total work - work done by AB
= 60 - 28 = 32
Remaining work / total work = 32 / 60 = 8 / 15
This method will take less time to compute guys...please try it.
(1)
Palak said:
5 years ago
Thanks all.
(1)
SAKSHI said:
2 days ago
Yes, It is 8/15.
(1)
Poorni said:
2 decades ago
Why (1 - 7/15)?
Mohideen said:
2 decades ago
@sundar.
Good explanation.
Good explanation.
Pravin Hambire said:
2 decades ago
Can you explain how 7/60 came?
Sunny guleria said:
2 decades ago
We have to calculate the remaining work after 4 dayz ,so why we subtract 1 dayz work from 4 day work? plz clear the question.
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