1. 80脳31/79绠渚胯繍绠楃瓑浜庡氩皯
80脳31/79=(79+1)脳31/79=31+31/79=31鍙31/79
2. 80×31/79用简便方法计算
80×31/79用简便方法计算=（79+1）×31/79=79×31/79+31/79=31+31/79=31又31/79