Write a composition about saving water, use the statistical knowledge learned in math class! In ten minutes,

Write a composition about saving water, use the statistical knowledge learned in math class! In ten minutes,

Limited water resources can not afford to be wasted. China is a serious water shortage country in the world. Many big cities have restricted water use, and Dingxi region in Gansu Province is famous for its drought and poverty. Zhangye is located in the Heihe River Basin, backed by the Qilian snow mountain. On the surface, there is no water shortage for the time being, but every year

What mathematical knowledge or models do I use when I go to bed?

It's time for our biological clock. It's a fixed model every day

Ask, online, common sense in mathematics
If heavy, construction will start on March 29, 2011
Until March 31, 2011, how many days has it been built?

3 days 29, 30, 31, or 2 days March 29 at 12:00