A: Thirty minutes. Because time is different from speed, there is no difference between speed and speed. It takes exactly 30 minutes, or half an hour, from 15: 40 to 16: 10 clockwise. These 30 minutes are very precious. Some people don't cherish it, but letting it go is always wasted, because time waits for no one and passes slowly. But some people cherish it and make full use of 30 minutes. Some people insist on practicing for 30 minutes every morning, some people insist on dancing for 30 minutes in square dance, and some people insist on practicing for 30 minutes in songs. Benefited a lot. So how precious 30 minutes is.