30/1+42/1+56/1+72/1 (综合算式)简便

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30/1+42/1+56/1+72/1 (综合算式)简便
30/1+42/1+56/1+72/1 (综合算式)简便

30/1+42/1+56/1+72/1 (综合算式)简便
你是不是分子分母打反了
1/30=1/(5*6)=1/5-1/6
1/42=1/(6*7)=1/6-1/7
1/56=1/(7*8)=1/7-1/8
1/72=1/(8*9)=1/8-1/9
所以1/30+1/42+1/56+1/72
=1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1/5-1/9=(9-5)/45=4/45

1/30+1/42+1/56+1/72+1/90 1/30+1/42+1/56+1/72+1/90 1/30+1/42+1/56+1/72 简算 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＝? 1/30+1/42+1/56+1/72= 30分之1+42分之一+56分之1+72分之一 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72 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+1/90 1/6+1/12+1/20+1/30+1/42+1/56+1/72 简便计算 1/2+1/6+1/20+1/30+1/42+1/56+1/72等于多少? 1/2+1/6+1/20+1/30+1/42+1/56+1/72等于几? 1/6+1/12+1/20+1/30+1/42+1/56+1/72 1/12+1/20+1/30+1/42+1/56+1/72+1/90=? 1/6+1/12+1/20+1/30+1/42+1/56+1/72=?