1/2乘1/3+1/3乘1/4+1/4乘1/5+……+1/99乘1/100=多少啊
问题描述：
1/2乘1/3+1/3乘1/4+1/4乘1/5+……+1/99乘1/100=多少啊
答
1/2×1/3+1/3×1/4+1/4×1/5+...+1/99×1/100
=(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+...+(1/99-1/100)
=1/2-1/3+1/3-1/4+1/4-1/5+...+1/99-1/100
=1/2-1/100
=49/100