Two pipes A and B can fill a tank in 12 hours and 15 hours respectivel...
A = 12 hours, B = 15 hours
Total work = LCM(12,15) = 60
So efficiency of A = 60/12 = 5, efficiency of B = 60/15 = 4
2 hrs work of (A+B) = 5+4 = 9
2*6(12) hours work of (A+B) = 9*6 = 54
So remaining work = 60-54 = 6
Now A’s turn at 13th hour, he will do remaining work(6) in 6/12 hr
So total 12 1/2 hrs
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Two pipes A and B can fill a tank in 12 hours and 15 hours respectivel...
Given:
- Pipe A can fill the tank in 12 hours.
- Pipe B can fill the tank in 15 hours.
- Pipes A and B are opened on alternate hours, with pipe A opened first.
To find: In how many hours the tank will be full.
Approach:
We can solve this problem using the concept of "work done". The work done by a pipe is proportional to the time it is opened and inversely proportional to the time it takes to fill the tank.
Let's assume that the tank has a capacity of 60 units (this is an arbitrary assumption, we can assume any value as long as we are consistent with our calculations).
- Pipe A can fill 60 units in 12 hours, so its work rate is 60/12 = 5 units per hour.
- Pipe B can fill 60 units in 15 hours, so its work rate is 60/15 = 4 units per hour.
Now, let's consider the filling of the tank when pipes A and B are opened alternately, starting with pipe A.
- In the first hour, pipe A fills 5 units.
- In the second hour, pipe B fills 4 units.
- In the third hour, pipe A fills 5 units.
- In the fourth hour, pipe B fills 4 units.
- And so on...
We can see that in every two hours, the total work done is 5+4=9 units.
To find the total time taken to fill the tank, we need to find how many times 2 hours go into 60 units. This can be done as follows:
- In 2 hours, 9 units are filled.
- In 4 hours, 18 units are filled.
- In 6 hours, 27 units are filled.
- In 8 hours, 36 units are filled.
- In 10 hours, 45 units are filled.
- In 12 hours, 54 units are filled.
- In 12 and a half hours, 57.5 units are filled.
- In 13 hours, 60 units are filled.
Therefore, the tank will be full in 13 hours.
Answer: Option (a) 13 hrs.
Two pipes A and B can fill a tank in 12 hours and 15 hours respectivel...
A = 12 hours, B = 15 hours
Total work = LCM(12,15) = 60
So efficiency of A = 60/12 = 5, efficiency of B = 60/15 = 4
2 hrs work of (A+B) = 5+4 = 9
2*6(12) hours work of (A+B) = 9*6 = 54
So remaining work = 60-54 = 6
Now A’s turn at 13th hour, he will do remaining work(6) in 6/12 hr
So total 12 1/2 hrs