9+99+999+9999+99999+999999=______.
9+99+999+9999+99999+999999=______.
计算:99999+9999+999+99+9=______.
99×9=891,999×9=8991,9999×9=______,999999×9=______.
简算:9999+999+99+9=______.
0.87×99+0.87=______×______.
巧填单位名称.1______-59______=1______;1______-9______=1______;1___
13×99+135×999+1357×9999=______.
写出数列9,99,999,9999,…的一个通项公式an=______.
125×(4+8)=______×______+______×______.
111111×999999=______.
填质数:21=______+______=______×______=______-______.
9升=______立方分米=______毫升.