奧數簡便運算題

9999×2222+3333×3334

=3333×6666+3333×3334

=3333×（6666+3334）

=33330000

20072007×2008-20082008×2007

=2007×10001×2008-2008×10001×2007

=0

123.123×234-234.234×123

=123×1.001×234-234×1.001×123

=0

3、89×4.4+0.611×44

=3.89×4.4+6.11×4.4

=（3.89+6.11）×4.4

=10×4.4

=44

0.111×3.7+0.777×0.9

=0.111×3.7+0.111×6.3

=0.111×（3.7+6.3）

=0.111×10

=1.11

0.9+9.9+99.9+999.9+9999.9

=10.8+99.9+999.9+9999.9

=1110.6+9999.9

=11110.5