3.999+0.999+2.999+9.9用简便方法计算
问题描述：
3.999+0.999+2.999+9.9用简便方法计算
答
3.999+0.999+2.999+9.9
=(4-0.001)+(1-0.001)+(3-0.001)+(10-0.1)
=(4+1+3)+10-3*0.001-0.1
=18-0.1-0.003
=17.897