The rate of emptying a pool is 1/20 pools per minute, and the rate of filling is 1/30 pools per minute. The speed difference is 1/60, which means it takes 60 minutes to empty a pool.

The second question:

At 12, the hour hand and the minute hand coincide, 60/(1-kloc-0/2) = 60 *12/11= 65 and 5//.

The next time is at 1: 05 and 5/1:00, that is, every 65 and 5/ 1 1: 00, that is, 6: 32 and 8/11.