横向
1
Single numeral from 0 to 9
3
Rectangle with four equal sides
4
Number divisible only by 1 and itself
5
Parts per hundred
9
U-shaped curve of a quadratic function
纵向
2
Rectangular array of numbers
3
Exact correspondence on both sides
6
Lines that never intersect
7
Math using letters for unknown values
8
The number representing nothing