用简便方法计算下面各题 1.66*21+19*21+85*19 2.36*111+888*8 99*99+199

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用简便方法计算下面各题 1.66*21+19*21+85*19 2.36*111+888*8 99*99+199

1:66×21+19×21+85×19
=(66+19)×21+85×19
=85×21+85×19
=85×(21+19)
=85×40
=3400
2:36×111+888×8
=36×111+111×64
=(36×64)×111
=11100
3:99×99+199
=99×99+99+100
=99×(99+1)+100
=99×100+100
=(99+1)×100
=100×100
=10000