Across
1
The number representing nothing
4
Sum divided by count
5
Reference line in a graph
6
Total distance around a shape
8
System of ordered marks for measuring
12
Space between two intersecting lines
Down
2
Divisible by two
3
Value that does not change
7
Split into equal parts
9
Three-sided polygon
10
Rectangle with four equal sides
11
U-shaped curve of a quadratic function
13
Parts per hundred