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问题: 数学

1+1/3+1/6+1/10+1/15+.....+1/(1+2+3+.....+100)的和是多少?

解答:

 1 + 1/3 + 1/6 + 1/10 + 1/15 + ... + 1/(1+2+3+.....+100)
= 2/(1*2) + 2/(2*3) + 2/(3*4) + 2/(4*5) + ... + 2/(100*101)
= 2 * [1/(1*2) + 1/(2*3) + 1/(3*4) + 1/(4*5) + ... + 1/(100*101)]
= 2 * (1/1-1/2 + 1/2-1/3 + 1/3-1/4 + 1/4-1/5 + ... + 1/100-1/101)
= 2 * (1/1 - 1/101)
= 200/101