99×9的简便方法计算

2024-11-22 20:12:36
推荐回答(5个)
回答(1):

99写为100-1
9写为10-1
再乘

回答(2):

=(100-1)*9
=100*9-1*9
=900-9
=891

回答(3):

99×9
=(100-1)×9
=900-9
=891

回答(4):

99*9
=9*(100-1)
=900-99
=891

回答(5):

1. 99×9
=(100-1)×9
=100×9-9
=900-9
=891
2. 99×9
=99×(10-1)
=99×10-99
=990-99
=891
3. 99×9
=(100-1)×(10-1)
=100×10-100-10+1
=1000-100-10+1
=891