算两次,是一种重要的数学方法,也被称为富比尼(G.Fubini)原理.学过列方程解应用题的同学们一定知道,“为了得到一个方程,我们必须把同一个量以两种不同的方法表示出来”(波利亚),即将同一个量“算两次”.算两次的典型做法是选择一个适当的量,从两个方面去考虑它,“一方面,另一方面,综合起来可得”.好像三步舞曲,这种舞曲常常在求解数学题的过程中听到.本文中仅从近几年江苏高考数学题中举出几例以供参考. Calculating twice is an important math method, also known as the G.Fubini principle.Students who have studied equations should know that in order to get an equation, we must A quantity is expressed in two different ways: “(Polygamy), about the same quantity” twice. “Calculating two times is typically a matter of choosing an appropriate quantity and considering it in two ways , ”On the one hand, on the other hand, on the other hand, it can be summed up." It seems like a three-step dance, which is often heard in the process of solving math problems. Several cases for reference.