Aptitude - Pipes and Cistern - Discussion
Discussion Forum : Pipes and Cistern - General Questions (Q.No. 15)
15.
Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours, C is closed and A and B can fill the remaining part in 7 hours. The number of hours taken by C alone to fill the tank is:
Answer: Option
Explanation:
| Part filled in 2 hours = | 2 | = | 1 |
| 6 | 3 |
| Remaining part = |  |
1 - | 1 |  |
= | 2 | . |
| 3 | 3 |
 (A + B)'s 7 hour's work = |
2 |
| 3 |
| (A + B)'s 1 hour's work = | 2 |
| 21 |
C's 1 hour's work = { (A + B + C)'s 1 hour's work } - { (A + B)'s 1 hour's work }
| = | |
1 | - | 2 | |
= | 1 |
| 6 | 21 | 14 |
C alone can fill the tank in 14 hours.
Discussion:
44 comments Page 4 of 5.
Abhishek said:
1 decade ago
@Sahil sharma see the options in the answer. No one options are below 6 hours so first we need to find 6 hours work.
We have 2 hours work. Now we need to find out 6 hours work.
We know 2*3=6. So multiply by 3 on RHS to find out 6 hours work. If we wanted to know 8 hours work then we need to do 2*4=8. If 10 hours then 2*5=10 and so on.
We have 2 hours work. Now we need to find out 6 hours work.
We know 2*3=6. So multiply by 3 on RHS to find out 6 hours work. If we wanted to know 8 hours work then we need to do 2*4=8. If 10 hours then 2*5=10 and so on.
Sahil sharma said:
1 decade ago
How 6 hrs are calculated here?
Arun said:
1 decade ago
Can't understand explain it clearly.
Soundharya saravanan said:
1 decade ago
A+B+C = 6 hrs after working 2 hrs.
A+B+C = 2 hrs.
So the remaining work is = 1-2/6 = 2/3.
A+B = 7 hrs.
(2/(3*7) = 2/21.
1/6-2/21 = 1/14.
Answer is: 14 hrs.
A+B+C = 2 hrs.
So the remaining work is = 1-2/6 = 2/3.
A+B = 7 hrs.
(2/(3*7) = 2/21.
1/6-2/21 = 1/14.
Answer is: 14 hrs.
Saranya said:
1 decade ago
Why 2/6?
Naveen said:
1 decade ago
(A+B)'s 7 hour work is 2/3.
(A+B)'s 1 hour work is(2/3)/7 = 2/3*7 = 2/21.
(A+B)'s 1 hour work is(2/3)/7 = 2/3*7 = 2/21.
Tamaghna said:
1 decade ago
What's the 1 hour calculation of (a+b+c)?
Harshitha said:
1 decade ago
Can you explain the step (A+B) 's 1 hour work = 2/21.
Vishaka said:
1 decade ago
How to calculate (A+B) in 7 hours ?
Nfl said:
1 decade ago
@Sharvari.
A+B+C = 2/6= 1/3 ..remaining part of cistern filled by A+B by 7 hours.
Remaining part 2/3 in 7 hours.. for exact 1 hour by A+B= 2/3*1/7=1/21.
A+B+C = 2/6= 1/3 ..remaining part of cistern filled by A+B by 7 hours.
Remaining part 2/3 in 7 hours.. for exact 1 hour by A+B= 2/3*1/7=1/21.
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