Question

69×42+59×42-42简便计算？

Answer 1

因为三个乘式中都有42，所以运用乘法分配律逆运算就是有42×（69+59-1）=5334

Answer 2

69×42+59×42-42
=69×42+59×42-1×42
=（69+59-1）×42
=127×42
=5334