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 11 of 35.
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;)
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.
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.
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.
Vinod said:
1 decade ago
Any one can explain me why we using remaining work 1-7/15 please.
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?
Sunil said:
1 decade ago
How that 60 came I can't got it?
Ram said:
1 decade ago
Hi friends..........
A can do wrk in 15 dayz ;
b Can do wrk in 20 dayz;
then LCM of A&B=7/60;
Explain:
=1/15+1/20
=[(4/4*15)+(3/3*20)]
=(4/60)+(3/60)
=3+4/60
=7/60
If A and B do wrk in 4 day=(7/60 *4 )
=7/15
work is 1 so=1-7/15
=15-7/15
Ans is = 8/15
Its easy for ur understanding...............
A can do wrk in 15 dayz ;
b Can do wrk in 20 dayz;
then LCM of A&B=7/60;
Explain:
=1/15+1/20
=[(4/4*15)+(3/3*20)]
=(4/60)+(3/60)
=3+4/60
=7/60
If A and B do wrk in 4 day=(7/60 *4 )
=7/15
work is 1 so=1-7/15
=15-7/15
Ans is = 8/15
Its easy for ur understanding...............
Santhi said:
1 decade ago
Good explanation swetha.
Bandna said:
1 decade ago
Good shweta.
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