1.9+19.9+199.9+1999.9+19999.9+0.5(用简便算法怎么算

1.9+19.9+199.9+1999.9+19999.9+0.5
=(1.9+0.1)+(19.9+0.1)+(199.9+0.1)+(1999.9+0.1)+(19999.9+0.1)
=2+20+200+2000+20000
=22222;

1.9+19.9+199.9+1999.9+19999.9+0.5
=2-0.1+20-0.1+200-0.1+2000-0.1+20000-0.1+0.5
=22222-0.5+0.5
=22222