我们知道，船从上游到下游是顺水航行，从下游到上游是逆水航行。数学上有些问题如果照题意叙述由后往前逆推算就显得很简单，这种解决问题的方法叫做还原法（倒推法）。下面的这道趣味题，就可以用“还原法”解答。[题目] 孙悟空从山上采来一堆仙桃。第一天，他先吃去其中的一 We know that the ship sails from upstream to downstream and from the lower reaches to the upper reaches is against the water. Some problems in mathematics, if according to the original narrative backwards from the forward reckoning it is very simple, this method of solving the problem is called the reduction method (pushback method). The following interesting topic, you can use the “reduction method” to answer. [Title] Monkey King from the mountain to take a bunch of Xiantao. On the first day, he ate one of them first