0.99*4+0.98*4+0.97*4+...0.91*4=?
问题描述:
0.99*4+0.98*4+0.97*4+...0.91*4=?
答
0.99*4+0.98*4+0.97*4+...0.91*4
=4*(0.99+0.91)*9/2
=34.2