Question

123.123*789-123*789.789的巧算？

Answer 1

因为123.123×789=789×（123+0.123）=789×123+789×0.123，123×789.789=123×（789+0.789）=123×789+123×0.789。所以原式等于789×123+789×0.123-（123×789+123×0.789）=0。

Answer 2

123.123×789-123×789.789
=123×1.001×789-123×789×1.001
=0

Answer 3

123×456÷789÷456×789÷123 =(123÷123)×(456÷456)×(789÷789)=1×1×1=1