1/78+1/91+1/105求答案

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1/78+1/91+1/105求答案
1/78+1/91+1/105求答案

1/78+1/91+1/105求答案
1/78+1/91+1/105
=(7+6)/(13×42)+1/105
=1/42+1/105
=5/210+2/210
=7/210=1/30

1/78+1/91+1/105
=1/13×﹙1/6+1/7﹚+1/105
=1/13×13/42+1/105
=1/42+1/105
=1/21×﹙1/2+1/5﹚
=1/21×7/10
=1/30.