999x21简便计算

2024-12-19 08:31:43
推荐回答(3个)
回答1:

298x21=,39X49=

回答2:

=(1000-1)X21
=1000X21-1X21
=21000-21
=20979

回答3:

=(1000-1)×21
=1000×21-1×21
=21000-21
=20979