89+899+8999+89999+899999 简便计算

2025-01-02 05:46:54
推荐回答(4个)
回答1:

89+899+8999+89999+899999
=90-1+900-1+...+900000-1
=90+900+...+900000-1*5
=999999-5
=999994

回答2:

解:
=(90-1)+(900-1)+(9000-1)+(90000-1)+(900000-1)
=999990-1-1-1-1-1
=999990-(1+1+1+1+1)
=999985

回答3:

89+899+8999+89999+899999

=90+900+9000+90000+900000-5
=999990-5
=999985

回答4:

90+900+9000+90000+900000-1-1-1-1-1
=999990-5
=999985