1/2+5/6+11/12+19/20.9890/9900 不是1/2+5/6+11/12+19/20.9899/9900 急
问题描述：
1/2+5/6+11/12+19/20.9890/9900 不是1/2+5/6+11/12+19/20.9899/9900 急
答
通过裂项可得出1/2+5/6+11/12+19/20...9890/9900=（1-1/2)+(1-1/6)+(1-1/12)……(1-1/9900)= 99 - (1/(1*2)+1/(2*3)……1/(99*100))= 99 - (1-1/2+1/2-1/3……1/99-1/100)= 99 - (1-1/100)= 99 - 99/100= 98又1/100 ...