浙江省中医院沈建平:30/1+42/1+56/1+72/1+90/1=?

来源：百度文库编辑：神马品牌网时间：2024/04/29 15:25:33

请写出主要过程.
哦,错了.
应该是1/30+1/42+1/56+1/72+1/90=?

是1/30+1/42+1/56+1/72+1/90吧

1/30+1/42+1/56+1/72+1/90
=1/(5*6)+1/(6*7)+1/(7*8)+1/(8*9)+1/(9*10)
=1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10
=1/5-1/10
=1/10

不会吧？这个还需要过程么？直接相加啊。
290

是输入错了吗?这不就是
30+42+56+72+90=290吗??

1/30+1/42+1/56+1/72+1/90
=1/5-1/6+1/6-1/7+1/7+1/8+1/8-1/9+1/9-1/10
=2/10-1/10
=1/10

是1/30+1/42+1/56+1/72+1/90吧等于1/10
＝84/2520+60/2520+45/2520+35/2520+28/2520
＝252/2520
＝1/10

巧算 1/30+1/42+1/56+1/72+1/90 30/1+42/1+56/1+72/1+90/1=? 20/1+30/1+42/1+56/1+72/1+90/1 1/20+1/30+1/42+1/56+1/72+1/90 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90= 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90=? 1/22+1/30+1/42+1/56+1/72+1/90=?简便方法是什么? 谁能巧算1-1/2-1/6-1/12-1/20-1/30-1/42-1/56-1/72-1/90 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90=______ 1/30+1/42+1/72+1/90+…1/9900