（1+1/2)(1+1/3)(1+1/4)(1+1/5)(1+1/6)(1+1/7)(1+1/8)(1+1/9)=?

题目

（1+1/2)(1+1/3)(1+1/4)(1+1/5)(1+1/6)(1+1/7)(1+1/8)(1+1/9)=?
我记得因为分子都是1所以应该有简便算法啊。

答案

（1+1/2)(1+1/3)(1+1/4)(1+1/5)(1+1/6)(1+1/7)(1+1/8)(1+1/9)
=(3/2)(4/3)(5/4)(6/5)(7/6)(8/7)(9/8)(10/9)
中间相同的约分
=10/2
=5