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1/30+1/42+1/56+1/72=

来源：学生作业帮 编辑：拍题作业网作业帮 分类：数学作业 时间：2024/06/05 17:51:32
1/30+1/42+1/56+1/72=
原式=1/(5×6)+1/(6×7)+1/(7×8)+1/(8×9)
=(6-5)/(5×6)+(7-6)/(6×7)+(8-7)/(7×8)+(9-8)/(8×9)
=6/(5×6)-5/(5×6)+7/(6×7)-6/(6×7)+8/(7×8)-7/(7×8)+9/(8×9)-8/(8×9)
=1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1/5-1/9
=9/45-5/45
=4/45
1/30+1/42+1/56+1/72+1/90 1/12+1/20+1/30+1/42+1/56+1/72+1/90=? 1/12+1/20+1/30+1/42+1/56+1/72= 等于多少? 1/30+1/42+1/56+1/72+1/90+1/110=? 1/30+1/42+1/56+1/72 简算1/30+1/42+1/56+1/72＝? 1/30+1/42+1/56+1/72＝ 1/30+1/42+1/56+1/72简便算法 1/30+1/42+1/56+1/72 简算 1/30+1/42+1/56+1/72+1/90=简便计算 20分之1+30分之1+42分之1+56分之1+72分之1=? 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+190+1/110=?