Question

用简便方法计算下面各题：（脱式）

Answer 1

0.9+0.99+0.999+0.9999+0.99999

=1-0.1+1-0.01+1-0.001+1-0.0001+1-0.00001

=5-0.11111

=4.88889

2.2+3.3+4.4+5.5+6.6+7.7+8.8+9.9

=1.1x(2+3+4+5+6+7+8+9)

=1.1x(2+9)x8/2

=1.1x44

=(1+0.1)x44

=44+4.4

=48.4