1-0.2+0.4-0.5+0.8-1.0+1.2-1.4+1.6-1.8+2怎么巧算

问题描述:

1-0.2+0.4-0.5+0.8-1.0+1.2-1.4+1.6-1.8+2怎么巧算

原式=(1-1.0)+(1.2-0.2)+(1.6+0.4)-(1.8-0.8)+(2-0.5-1.4)
=0+1+2+-1+0.1
=2+0.1
=2.1