Three boys can go on a circular pathway in `3min 20sec, 3min 40 sec and 4 min` respectively. If they start simultaneously from same place and at the same time, when will they meet next?

Three taps A,B and C fill a tank in 20 min, 15 min and 12 min, respectively. If all the taps are opened simultaneously, how long will they take to fill 40% of the tank?

Pipe A and pipe B can fill up a tank in 40 min and 80 min respectively Both the pipes are opened simultaneously for some time and then pipe B is closed. If the total time to fill up the tank is 30 minutes then how long the pipe B was open for ?

Two pipes A and B can fill a cistern in 30 min and 40 min respectively. Both the pipes are turned on simultaneously. When should the second pipe be closed if the cistern is to be filled in 24 min.

Three bells, toll at interval of 36 sec, 40 sec and 48 sec respectively. They start ringing together at particular time. They next toll together after:

Two pipes, A and B, can fill an empty cistern in 20min and 40min, respectively. Both the pipes are opened together, and after some time, pipe A is closed. If the cistern gets filled in 30 min, then for how long was pipe A kept open?

Seven bell sring at intervals of 2,3,4,6,8,9 and 12 min,respectively.They started ringing simultaneously at 5:00 in the morning. What will be the next time when they all ring simultaneously?