简便计算 1又1/3-7/12+9/20-11/30+13/42-15/56

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简便计算 1又1/3-7/12+9/20-11/30+13/42-15/56

简便计算 1又1/3-7/12+9/20-11/30+13/42-15/56
简便计算 1又1/3-7/12+9/20-11/30+13/42-15/56

简便计算 1又1/3-7/12+9/20-11/30+13/42-15/56
1又1/3-7/12+9/20-11/30+13/42-15/56
=1+1/3-﹙1/3+1/4﹚+﹙1/4+1/5﹚-﹙1/5+1/6﹚+﹙1/6+1/7﹚-﹙1/7+1/8﹚
=1+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8
=1-1/8
=7/8

7/12=1/3+1/4;
9/20=1/4+1/5.........
原式为1+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8=1-1/8=7/8

原式=1-1/3-(1/3+1/4)……-(1/7+1/8)
=1-1/8
=7/8