众所周知:所谓“牛吃草”问题,就是一类工作总量不固定(均匀变化)的问题.解决这类问题的一般常用方法大概有以下几种,现分别举例如下,仅供参考.例1一片草地均匀地生长,可供27头牛吃6天,可供23头牛吃9天,问可供21头牛吃多少天?(注:假设每头牛每天吃草量 It is well-known that the so-called “cattle grazing” problem is a type of problem where the total amount of work is not fixed (uniform change). The general methods commonly used to solve such problems are as follows, and are given below for reference purposes only. Example 1 A uniform growth of grass for 27 cows to eat for 6 days for 23 cows for 9 days and ask for 21 cows for how many days? (Note: Assuming each cows graze daily