Across
1
Rectangle with four equal sides
3
Lines that never intersect
5
The number representing nothing
6
Collection of distinct elements
7
Value that does not change
8
Divisible by two
9
Total distance around a shape
Down
2
Number divisible only by 1 and itself
3
Number greater than zero
4
Steepness of a line
10
Difference between highest and lowest values
11
Single numeral from 0 to 9