题目

Food is very important. Everyone needs to eat well if he or she wants to have a strong body. Our minds(头脑) also need a kind of food. This kind of food is knowledge.We begin to get knowledge even when we are very young. Small children are interested in everything around them. They learn something while they are watching and listening. When they are getting older, they begin to read story books, science books …, anything they like. When they find something new, they love to ask questions and try to find out answers. What is the best way to get knowledge? If we learn by ourselves, we will g已知等腰三角形的两边长分别为2和5，则它的周长是_______