题目

如图，图中A、B、C、D四点是某厂的四个生产车间，现在要厂里建一个仓库，使仓库到A、B、c、D四个生产车间的距离的和最小．问仓库应建在何处? 答案：解：如图，仓库应建在对角线AD与BC的交点P处．下面证明PA+PB+PC+PD是最小的．设点 P′ 异于P点，要证明，PA+PB+PC+PD< P′A+ P′B+ P′C+ P′D，在△ P′ BC中，BC< P′C+ P′B，即PB+PC< P′C+ P′B．在△ P′AD中，AD< P′A+ P′D，即PA+PD< P′A+ P′D．相加得，PA+PB+PC+PD< P′ A+ P′B+ P′C+ P′D．所以P点是所求单词拼写Project Hope helps people in the poor area build schools. It also helps poor 1. c______ go to school. China’s Project Hope has raised lots of 2. m every year. It has helped more than 2.5 million poor students 3. s_____it was set up over 20 years ago. So far, the project has collected more than 2.2 billion yuan from China and 4. o_____ countries in the world. The money has been used in the building of many Project Hope primary schools.About 80 percent of the Project Hope schools are in China’s middle and 5. w____ areas, because they are still developing.Project Hope has helped to 6. b faraway learning centers, libraries and video centers. It also helped train school teachers from poor areas.Of all the non-government welfare（福利）projects, Project Hope has become the 7. l______ one so far in China. People say that still about 40 million primary school students 8. n____ help around the country, including 34 million primary, junior, and high school students. Mr Gao, one of the 9. w_____ in Project Hope said the organization would 10.t______ to raise more money and help more students in the future.