Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 2)
2.
A can lay railway track between two given stations in 16 days and B can do the same job in 12 days. With help of C, they did the job in 4 days only. Then, C alone can do the job in:
Answer: Option
Explanation:
| (A + B + C)'s 1 day's work = | 1 | , |
| 4 |
| A's 1 day's work = | 1 | , |
| 16 |
| B's 1 day's work = | 1 | . |
| 12 |
 C's 1 day's work = |
1 | - |  |
1 | + | 1 |  |
= | |
1 | - | 7 | |
= | 5 | . |
| 4 | 16 | 12 | 4 | 48 | 48 |
| So, C alone can do the work in | 48 | = 9 | 3 | days. |
| 5 | 5 |
Discussion:
224 comments Page 5 of 23.
Suryakiran varma said:
1 decade ago
Look,
A can do a work in 16 days,so his one day work will be=1/16
and also B's one day work will be =1/12;
in the same way A,B,C together do a work in 4 days,so thier one day work will be=1/4
C 's one day work will be=(A+B+C)'s one day work - (A+B)'s one day work
i.e..
=(1/4)-(1/16+1/12)
=(1/4)-(7/48)
=(5/48)
thus,C's one day work is = 5/48,
so,he can do the work in 48/5 days..i.e..9 3/5.
A can do a work in 16 days,so his one day work will be=1/16
and also B's one day work will be =1/12;
in the same way A,B,C together do a work in 4 days,so thier one day work will be=1/4
C 's one day work will be=(A+B+C)'s one day work - (A+B)'s one day work
i.e..
=(1/4)-(1/16+1/12)
=(1/4)-(7/48)
=(5/48)
thus,C's one day work is = 5/48,
so,he can do the work in 48/5 days..i.e..9 3/5.
Hiren said:
1 decade ago
Why you write 48/5 from 5/48.
Amit.J said:
1 decade ago
A+B+C=4 day.
A=16 day.
B=12 day.
C=?
Formula..
A+B+C=A*B*C/AB+BC+CA
4=192C/192+28C
4(192+28C)=192C
768+112C=192C
768=192C-112C
768=80C
768/80=C
C=48/5 Ans.
A=16 day.
B=12 day.
C=?
Formula..
A+B+C=A*B*C/AB+BC+CA
4=192C/192+28C
4(192+28C)=192C
768+112C=192C
768=192C-112C
768=80C
768/80=C
C=48/5 Ans.
Parthasarathy said:
1 decade ago
@HIREN.
If A can do some work in N days.
So A can do that same work in one day =1/N.
So the answer 5/48 obtained by (1/4) - (1/16+1/4) =5/48.
So you should consider this as only 48/5.
If A can do some work in N days.
So A can do that same work in one day =1/N.
So the answer 5/48 obtained by (1/4) - (1/16+1/4) =5/48.
So you should consider this as only 48/5.
Pradeep said:
1 decade ago
Thank you aparna.
Kalai said:
1 decade ago
I can't understand how 5/48 becomes 48/5. Can you clarify for me.
Shiyamala said:
1 decade ago
A=1/16;
B=1/12;
A+B=[1/16+1/12]
=[16+12/192]{1/16*12/12=16/192;1/12*16/16=16/192)
=28/192
=7/48 {4*7=28; 48*4=192)
C-[A+B]=1/4-7/48 {1/4*12/12=12/48)
=12-7/48
=5/48
but c work alone.so,48/5=9*3/5
B=1/12;
A+B=[1/16+1/12]
=[16+12/192]{1/16*12/12=16/192;1/12*16/16=16/192)
=28/192
=7/48 {4*7=28; 48*4=192)
C-[A+B]=1/4-7/48 {1/4*12/12=12/48)
=12-7/48
=5/48
but c work alone.so,48/5=9*3/5
Ajay jabalpur said:
1 decade ago
@Hiren.
If A's one day work = 1/n, then A can finish the work in n/1 days.
Similarly,
C's one day work is 5/48, then C can finish the work in 48/5 days.
If A's one day work = 1/n, then A can finish the work in n/1 days.
Similarly,
C's one day work is 5/48, then C can finish the work in 48/5 days.
Twinkle said:
1 decade ago
A+B+C=1/4.
[1/16]+[1/12]+C=[1/4].
C=0.1041.
THEREFORE, 1/0.1041=48/5.
i.e: 9*3/5.
[1/16]+[1/12]+C=[1/4].
C=0.1041.
THEREFORE, 1/0.1041=48/5.
i.e: 9*3/5.
Sudha said:
1 decade ago
At the end of explanation,
C's 1 day work is 5/48 I calculated up to to this but how it comes work in 48/5 days.
Because acc. to formula if A's 1 day work is 1/n' then A can finish work in n' days.
Means only it comes 48. I am just confuse. please explain me.
C's 1 day work is 5/48 I calculated up to to this but how it comes work in 48/5 days.
Because acc. to formula if A's 1 day work is 1/n' then A can finish work in n' days.
Means only it comes 48. I am just confuse. please explain me.
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