简便计算; 1.9+1.99+1.999+1.9999+1.99999 28*1111+9999*8
问题描述：
简便计算; 1.9+1.99+1.999+1.9999+1.99999 28*1111+9999*8
答
1.9+1.99+1.999+1.9999+1.99999
= 2-0.1 + 2-0.01 + 2- 0.001 +2- 0.0001 +2- 0.00001
= 10- 0.11111
= 9.88889
28*1111+9999*8
= 28*1111+ 1111*9*8
= 1111*(28+72)
= 1111*100
= 111100