Question

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

Answer 1

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;