几道算术题···············要用简便算法

题目

几道算术题···············要用简便算法
1.1/2 +1/6+1/12 +1/20+1/30+1/42
2.0.84+3又1/3+0.2+6又2/3*0.48

答案

1) 1/2 = 1/1 - 1/2,1/6 = 1/2 - /3,1/12 = 1/3 - 1/4……所以加减合并之后变成了：(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7) = 1 - 1/7 = 6/7.
2)暂无