原式=1/2+1/6+1/12+1/20+1/30+……+1/110
=1/1*2+1/2*3+1/3*4+……+1/11*10
=(1/1-1/2)+(1/2-1/3)+……+(1/10-1/11)
=1-1/2+1/2-1/3+1/3-...+1/10-1/11
=1-1/11
=10/11
解：原式=1/(1*2)+1/(2*3)+1/(3*4)+...+1/(10*11)
=1-1/2+1/2-1/3+1/3-1/4...+1/10-1/11
=1-1/11
=10/11
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