Question

22乘以20.1减去21乘以19.9简便方法？

怎么简便

Answer 1

22×20.1-21×19.9
=（21+1）×20.1-21×19.9
=21×（20.1-19.9）+20.1
=21×0.2+20.1
=4.2+20.1
=24.3

Answer 2

22×20.1-21×19.9
=22×(20+0.1)-21×(20-0.1)
=22×20+22×0.1-21×20+21×0.1
=(22-21)×20+(22+21) ×0.1
=20+4.3
=24.3

Answer 3

原式=21*20.1-21*19.9+1*20.1
=21*(20.1-19.9)+20.1
=21*0.2+20.1
=4.2+20.1
=24.3

Answer 4

22x20.1-21x19.9
=22x（20+0.1）-21x（20-0.1）
=22x20+22x0.1-21x20+21x0.1
=（22x20-21x20）+(22x0.1+21x0.1)
=20x（22-21）+0.1x（22+21）
=20+4.3
=24.3