1. 80脳31/79綆渚胯繍綆楃瓑浜庡氬皯
80脳31/79=(79+1)脳31/79=31+31/79=31鍙31/79
2. 80×31/79用簡便方法計算
80×31/79用簡便方法計算=（79+1）×31/79=79×31/79+31/79=31+31/79=31又31/79