《2025年智趣夏令营玩转数学五年级通用版》

18. 已知$1-\frac {1}{2}=\frac {1}{2},\frac {1}{2}-\frac {1}{3}=\frac {1}{6},\frac {1}{3}-\frac {1}{4}=\frac {1}{12},\frac {1}{4}-\frac {1}{5}=\frac {1}{20},\frac {1}{5}-\frac {1}{6}=\frac {1}{30}... ... $你能很快算出$\frac {1}{2}+\frac {1}{6}+\frac {1}{12}+\frac {1}{20}+\frac {1}{30}+\frac {1}{42}+\frac {1}{56}+\frac {1}{72}+\frac {1}{90}$的结果吗? 结果是$\frac{9}{10}$

答案： $\frac{9}{10}$