1/2+1/6+1/12+1/20+......1/110=?

Answer 1

1/2+1/6+1/12+1/20+......1/110
=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+....+1/(10*11)
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+........+1/10-1/11
=1-1/11
=10/11

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