一道分数简便计算题目
- 时间:2020-06-17 18:43:17
- 分类:数学世界
- 阅读:97 次
分享一道分数简便计算题目:1/(5×8)+1/(8×11)+1/(11×14)+1/(14×17)+……+1/(95×98)+1/(98×101)=?看到这个简便计算问题,不由得想起以前做过的1/(1×2)+1/(2×3)+1/(3×4)+1/(4×5)+……+1/(98×99)+1/(99×100)=?,当时是根据1/(1×2)=1-1/2,1/(2×3)=1/2-1/3,……把原题转化为:1-1/2+1/2-1/3+1/3-1/4+1/4-……+1/99-1/100,然后抵消中间的数,仅保留首尾,变成1-1/100=99/100。
今天这道题目的形式与原来那题很像,但也有不同的地方,即分母中相乘的两个数并不相邻,而是相差3,所以解题的方法就要发生相应的变化。先来看看其中一个加数吧!1/(5×8)=1/40,而1/5-1/8=3/40;1/(8×11)=1/88,1/8-1/11=3/88。也就是1/(5×8)并不等于1/5-1/8,而是等于(1/5-1/8)×1/3,其他加数也同样如此,这样我们便可以找出简便计算的方法了。请看下面的计算过程:
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