123 9 82 8 47 7用简便方法

9等于8与1的和，7等于8与1的差，原算式可以看作123乘以8与1的和之积加上82乘以8的积只和加上47乘以8与1的差之积的和，计算过程如下：

123x9+82x8+47x7

=123x(8+1)+82x8+47x(8-1)

=123x8+123+82x8+47x8-47

=184+123+656+336-47

=184+656+123+336-47

=840+123+336-47

=963+336-47

=1299-47

=1252