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 7 of 23.
TRUPTIMAYEE BAHINIPATI said:
7 years ago
The solution in LCM method is;
Solution :
SUPPOSE TOTAL WORK=1UNIT.
A=15d L.C.M. of 15,20=60.
B=20d.
Then A=4.
B=3.
A+B=7unit=60.
4 unit=60/7*1/4=15/7day.
1day work of A+B=7/15unit.
Remaining work=1-7/15=8/15 unit left (Ans.)
Solution :
SUPPOSE TOTAL WORK=1UNIT.
A=15d L.C.M. of 15,20=60.
B=20d.
Then A=4.
B=3.
A+B=7unit=60.
4 unit=60/7*1/4=15/7day.
1day work of A+B=7/15unit.
Remaining work=1-7/15=8/15 unit left (Ans.)
Imran said:
7 years ago
Can anyone explain me this question by LCM method?
Justine said:
7 years ago
How come that 48 gets retain? when you cross multiply 48/1 * 1/16 = 3 and 48/1 * 1/12 = 4?
Please explain me.
Please explain me.
Pavani said:
7 years ago
(A+B+C)'s efficiency - (A+B)'s efficiency = C's efficiency.
(1/4) - (1/16+1/12) = C's efficiency.
5/48 = C's efficiency.
So, the time taken, to complete the total work, by C = 48/5= 9 3/5.
(1/4) - (1/16+1/12) = C's efficiency.
5/48 = C's efficiency.
So, the time taken, to complete the total work, by C = 48/5= 9 3/5.
Vikas said:
7 years ago
1/4-7/48= 5/48 how? Please explain.
Ritesh Raj said:
7 years ago
@All.
Check this;
A-16d
B-12d
C-xd.
Lcm of all 3=48x(let it be total work that they have to complete).
Now efficiency ( of A,B,C is 3x,4xand 48 resp)
Now. on 1st day all 3 together can do 3x+4x+48 works it is given that they together complete the work in 4 days so;
4*(3x+4x+48)=48 solve it get x, then you will get the answer.
Check this;
A-16d
B-12d
C-xd.
Lcm of all 3=48x(let it be total work that they have to complete).
Now efficiency ( of A,B,C is 3x,4xand 48 resp)
Now. on 1st day all 3 together can do 3x+4x+48 works it is given that they together complete the work in 4 days so;
4*(3x+4x+48)=48 solve it get x, then you will get the answer.
Vaishu said:
7 years ago
How did 1/4 become total one day's work?
Appu said:
8 years ago
Thanks @Aparna.
Manish said:
8 years ago
@ALL.
a&b's work for 4 days=7/12.
bal is c work =1-7/12=5/12.
c's 5/12 work in 4 days.
Therefore- 1 work ie 100 % work in how many days?
5/12 in 4 days.
1 in how many days.
4*12/5=48/5 days.
Fraction= 9*3/5.
a&b's work for 4 days=7/12.
bal is c work =1-7/12=5/12.
c's 5/12 work in 4 days.
Therefore- 1 work ie 100 % work in how many days?
5/12 in 4 days.
1 in how many days.
4*12/5=48/5 days.
Fraction= 9*3/5.
Ved Prakash Singh said:
8 years ago
A's one day work=1/16.
B's one day work=1/12.
Let C can finish the work in x days hence C's one day work=1/x.
A, B and C together can finish the work in 4 days and total work is 1.
4/16+4/12+4/x=1.
so x=48/5 =>9*3/5.
B's one day work=1/12.
Let C can finish the work in x days hence C's one day work=1/x.
A, B and C together can finish the work in 4 days and total work is 1.
4/16+4/12+4/x=1.
so x=48/5 =>9*3/5.
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