找基准数来求解,化繁为简,节约用纸

in #steempress5 years ago

昨天晚上看到儿子在做一道数学题,算得不亦乐乎,草稿纸写了一大截,还念念有词地说:“ 这么简单的题目,还想难倒我?!

我走近一看,把我乐坏了。

题目很长,是这样的:

93 + 92 + 88 + 89 + 90 + 86 + 91 + 87 =

两位数的加法,确实不难,但是数字很多,儿子在纸上一个一个数字加起来,列算式列了好长。

等儿子做完,把答案 716写在作业本上以后,我便坐下来对他说:

儿子,你做的很好,过程很细心,这么多数字相加,答案也算对了,真的很棒呢!不过,做这种题目还有一个简单的方法,你想不想知道啊?

儿子迫不及待地说:想知道想知道!

接下来,我就教了他这个方法:

用找基数的方法进行简便运算:

这种方法适用于一串数字差不多,且都和某数接近的运算。

以上题为例,仔细观察一下,8个数字很接近,都在90附近,所以,我们定下这个数列的基数为90。

接下来,做法就很简单了,不用多讲,上步骤就一目了然了:


就这样,儿子快写满一页草稿纸的题目,直接在作业本上写3行过程,就能心算出结果。

儿子很崇拜地看着我,我便趁着这个机会又教育了他一番:

看到题目时,不要急于求解,而是要找到题目的规律。不要怕浪费时间,花时间分析题面,找到规律以后再做,反而会节省很多时间,不但避免了解题过程中的粗心大意可能带来的错误,还节约了草稿纸!

儿子很开心的说:我记住了!

哈哈,我对于自己这个Dad的教育方式还是很满意的,你觉得呢?



Posted from my blog with SteemPress : https://arch-deletion.000webhostapp.com/2019/01/%e6%89%be%e5%9f%ba%e5%87%86%e6%95%b0%e6%9d%a5%e6%b1%82%e8%a7%a3%ef%bc%8c%e5%8c%96%e7%b9%81%e4%b8%ba%e7%ae%80%ef%bc%8c%e8%8a%82%e7%ba%a6%e7%94%a8%e7%ba%b8
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