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:
344 comments Page 30 of 35.
Sunil said:
1 decade ago
How that 60 came I can't got it?
Niruban said:
1 decade ago
A does the work for a day and B does it for a same day. If we add both then it should be work done for 2 days but why is it considered as one day work?
Vinod said:
1 decade ago
Any one can explain me why we using remaining work 1-7/15 please.
Santosh said:
1 decade ago
@Pravin Hambire
Q. How 7/60 came ?
See 1/15 +1/20
Now find the lcm of 15 and 20, it is 60.
Now if you divide 60 by 15 quotient is 4. So mulitply 1/15 with 4, it will become 4/15 .
Again divide 60 by 20. Quotient is 3, now multiply 1/20 with 3. It will become 3/20.
Now you alredy know that lcm of 15 nd 20 is 60. So write 60 in denominator.
Now add the quotient which is 3 nd 4 and write it in numerator.
So finally 7/60 .
Hope you got it.
Q. How 7/60 came ?
See 1/15 +1/20
Now find the lcm of 15 and 20, it is 60.
Now if you divide 60 by 15 quotient is 4. So mulitply 1/15 with 4, it will become 4/15 .
Again divide 60 by 20. Quotient is 3, now multiply 1/20 with 3. It will become 3/20.
Now you alredy know that lcm of 15 nd 20 is 60. So write 60 in denominator.
Now add the quotient which is 3 nd 4 and write it in numerator.
So finally 7/60 .
Hope you got it.
Ghhhhgh said:
1 decade ago
Here it is given that A can do a piece of work in 15 days.
So now we can find the A's 1 day work whicvh is =1/15.
So now we can find the A's 1 day work whicvh is =1/15.
James said:
1 decade ago
We can solve this problem more easily by taking efficiency.
Since work=efficiency *time
To take efficiency take lcm of A&B.it is 60
60/15=4 60/20=3
A'efficiency=4 & B's=3
Work=4*15 or 3*20 =60
Work=60
Since a b works together for 4 days
a+b effi=4+3=7
7*4=28
Total work-work done
60-28=32(work remaining)
32/60=8/15.
Since work=efficiency *time
To take efficiency take lcm of A&B.it is 60
60/15=4 60/20=3
A'efficiency=4 & B's=3
Work=4*15 or 3*20 =60
Work=60
Since a b works together for 4 days
a+b effi=4+3=7
7*4=28
Total work-work done
60-28=32(work remaining)
32/60=8/15.
Rahul said:
1 decade ago
Ok.
I guess the easier way to explain this is to subtract(20days-14days)= 5 days,
We have calculated for 4 days, therfore remaining is 1;)
I guess the easier way to explain this is to subtract(20days-14days)= 5 days,
We have calculated for 4 days, therfore remaining is 1;)
Swetha said:
1 decade ago
@Sri harsha.p
It is not very long process..it is short method only.i explained every steps.,so only it looks like long process.
It is not very long process..it is short method only.i explained every steps.,so only it looks like long process.
Ramkumar said:
1 decade ago
Nice work swetha.
SRI HARSHA.P said:
1 decade ago
The way said by swetha is very long process.
that wastes time in the exam hall.
thats not the good way to do the problem.
always prepare for ashort method.
Short method takes time for the first time by practice it gives u TIME MANAGEMENT. So better to practice SM.
that wastes time in the exam hall.
thats not the good way to do the problem.
always prepare for ashort method.
Short method takes time for the first time by practice it gives u TIME MANAGEMENT. So better to practice SM.
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