同学们经常会遇到这样一类的应用题:已知条件中某个(些)数量不具体或问题与条件之间的关系比较复杂。解这类应用题最好的方法是巧妙地设一个数,从而使问题得到解决。 Students often encounter such a class of application questions: the known conditions of some (some) the number of unspecific or problem and the relationship between the conditions is more complicated. The best way to solve such problems is to skillfully set a number so that the problem can be solved.