一、故事引入古时候,我们的祖先住在山洞里,以打猎为生。那时候没有纸和笔,他们就用树枝把每天打的猎物的数量记在洞壁上。第一天打了一只兔子,他们就在洞壁上写了个“1”;第二天打了1只兔子和两只野鸡,就在洞壁上写上个“3”;第三天打了5只狐 First, the introduction of the story In ancient times, our ancestors lived in the cave, to hunt for a living. At that time without paper and pen, they use the branches to record the number of prey hit daily on the wall. The first day of a rabbit, they wrote a “1” on the wall; the next day hit a rabbit and two pheasants, on the wall to write a "3 ; The third day hit five foxes