Across
1
The number representing nothing
2
Total distance around a shape
7
Reference line in a graph
8
System of ordered marks for measuring
9
Number divisible only by 1 and itself
10
Line crossing from corner to corner
11
Comparison of two quantities
12
Collection of distinct elements
Down
2
Number greater than zero
3
Steepness of a line
4
Sum divided by count
5
Rectangular array of numbers
6
Part of a circle's circumference