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列一元一次方程解应用题是一个重点内容,对同学们来说更是一个难点.其难有二:一是如何选设未知数;二是找相等关系.本文就选设未知数这一问题举例说明常见的三种方法,以帮助同学们突破难点.一、直接设元即问(求)什么就设什么,这是解应用题常用的方法.只要题中的数量关系能用未知量明显地表示出来时,就可采用此法.例1小明参加数学竞赛,共10道题,每答对1道题得5分,答错或不答要倒扣3分.小明只得了2分,他答对了几道题呢?分析此题中的数量关系很明显,只要知道了答对的题数,就可得出答错或不答的
It is a difficult task for students to solve the problem of solving one-liner equations. It is hard to find two solutions: one is how to choose the unknown; the other is to find the equal relationship. Common three ways to help students break through the difficulties. First, directly set the element that is asked what (what) is set, which is commonly used method of solving problems .As long as the problem of quantitative relationship can be clearly expressed with the unknown Example 1 Xiaoming participate in mathematics contest, a total of 10 questions, each answer to a question 5 points, wrong answer or do not want to deduct 3 points Xiao Ming had only 2 points, he answered correctly A few questions? Analysis of the number of questions in this relationship is obvious, as long as you know the answer to the question number, you can get the wrong answer or not