56*78,21*47怎样简便运算_数学解答

56*78,21*47怎样简便运算

人气：400 ℃　时间：2019-12-07 07:25:27

解答

56x78
=(50+6)x(80-2)
=4000-100+480-12
=4368
21x47
=(20+1)x(50-3)
=1000-60+50-3
=987