Across
1
Single numeral from 0 to 9
4
Number divisible only by 1 and itself
5
Reference line in a graph
7
Math using letters for unknown values
11
Value that does not change
13
Lines that never intersect
Down
2
Difference between highest and lowest values
3
Number that divides evenly into another
4
Number greater than zero
6
Distance from center to edge of circle
8
Divisible by two
9
System of ordered marks for measuring
10
Result of addition
12
Number less than zero