201x42－42简便计算是怎么算的

Question

如题所述

Answer 1

（201减1）×42就行了，等于8400

Answer 2

=（200+1）x42-42=200x42+42-42=200x42=8400

Answer 3

201x42－42
=42×(201-1)
=42×200
=8400

Answer 4

=200x42
=8400