 Hello and welcome to the session. In this session we discussed the following question which says pipe A can fill a system in 5 hours and pipe B can fill it in 7 hours. Both the pipes are open and after 2 hours pipe A is closed. How much time will B take to fill the remaining part of the tank? Let's proceed with the solution now. Now time taken by pipe A to fill the system is 5 hours then time taken by pipe B to fill the system is equal to 7 hours. Now let's find out the work done by pipe A in 1 hour and this would be equal to 1 upon 5. Now work done by pipe B in 1 hour would be equal to 1 upon 7. Now the total work done by pipes A and B together in 1 hour is equal to the work done by pipe A in 1 hour that is 1 upon 5 plus work done by pipe B in 1 hour that is 1 upon 7. And this is equal to 12 upon 35. So work done by the pipes A and B together in 1 hour is equal to 12 upon 35. Now both the pipes are open and after 2 hours the pipe A was closed. So now we will find out the work done by pipes A and B together in 2 hours and this would be equal to work done by pipes A and B in 1 hour that is 12 upon 35 multiplied by 2 which would be equal to 24 upon 35. So this means pipe A and B together can fill up the 24 upon 35 part of the tank in 2 hours. Now the remaining part of the tank would be equal to 1 minus 24 upon 35 and this would be equal to 11 upon 35. So this means 11 upon 35 part of the tank needs to be filled. We are supposed to find the tank taken by B to fill the remaining part of the tank which is 11 upon 35. Now we have work done by pipe B in 1 hour is 1 upon 7. So this means that 1 upon 7 part of the tank is filled by the pipe B in 1 hour. So this means 11 upon 35 part of the tank is filled by pipe B in 7 into 11 upon 35 hours and this would be equal to 77 upon 35 hours. So 11 upon 35 part of the tank that is the remaining part of the tank is filled by the pipe B alone in 77 upon 35 hours. 7 11 times is 77 and 75 times is 35 so this is equal to 11 upon 5 hours or you can say 2 1 upon 5 hours is the time taken by B alone to fill the remaining part of the tank. So the final answer is 2 1 upon 5 hours. So this completes the session. Hope you have understood the solution for this question.