Across
1
Single numeral from 0 to 9
3
System of ordered marks for measuring
4
The number representing nothing
5
Sum divided by count
8
Corner point of a polygon
11
Symbol representing unknown value
Down
2
Number less than zero
3
Exact correspondence on both sides
6
Total distance around a shape
7
Three-sided polygon
9
Middle value in an ordered dataset
10
Power to which a number is raised