黄冈小状元页21四年级数学优秀。作业:用简单的方法计算下面的问题。

=66×21+19×21+85×(21-2)

=66×21+19×21+85×21-85×2

=(66+19+85)×21-85×2

=160×21-170

=3190

(2)36×111+888×8

=36×111+111×(8×8)

=36×111+111×64

=111×(64+36)

=11100

(3)99×99+199

=99×(100-1)+199

=9900-99+199

=9900+(199-99)

=10000