Across
1
Three-sided polygon
3
Number greater than zero
4
Rectangular array of numbers
6
Difference between highest and lowest values
8
Line touching circle at one point
10
Number with digits after a point
11
Comparison of two quantities
12
Math using letters for unknown values
13
Exact correspondence on both sides
Down
2
Number divisible only by 1 and itself
3
Parts per hundred
5
Middle value in an ordered dataset
7
Proven mathematical statement
9
The number representing nothing