2. In order to meet the water demand, the water storage capacity should be greater than or equal to the water consumption. In the time of using water at the same time, water storage and water use should be balanced, and water storage should only be carried out when enterprises do not use water. This part needs water before 9 o'clock the next day, so the water level is the highest at 9 o'clock in the evening.
3. Look at the slowest car in the circle. One car came back on the first lap and the other was halfway. The second lap came back just in time, so it took 10 minutes.
4. Not a sharp turn, just 10-2- 1=7.
5. there are a, red x, yellow y and green z balls. A-2=X，A-2=Y，A-2 = Z； x+Y+Z = A； A=3 after being brought in.
6.？
7. According to the meaning of the question, it can be concluded that A lost 3 1 for the first time and 37/for the second time, and B doesn't know whether it was all lost or not.
If you want to know how many times, you must wait until you stop knocking, which means a delay of 3 seconds. 12 will wait until 12*3=36 seconds, and 6*3= 18 seconds at 6 o'clock.
9. Set the difference X, 2X+30+X=( 12-8)*60, X=70 minutes.
10. 1*2P=A，A/2= 1*2P/2=2(P- 1)，P=60，P- 1=59