二分之一+六分之一+十二分之一+二十分之一+三十分之一+四十二分之一+五十六分之一+七十二?D

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1/2+1/6+1/12+1/30+1/42+1/56+1/72
=(1-1/历亏租2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)+(1/8-1/肢兆9)
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/空扮6+1/6-1/7+1/7-1/8+1/8-1/9
=1-1/9
=8/9

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