Across
1
Rectangular array of numbers
5
Amount of space an object occupies
7
Symbol representing unknown value
9
The number representing nothing
Down
2
Result of addition
3
Part of a circle's circumference
4
Line crossing from corner to corner
6
Corner point of a polygon
8
Single numeral from 0 to 9
10
Three-sided polygon
11
Part of a whole number
12
Number divisible only by 1 and itself