GAUSS8 2007 Problem 24

A lattice point is a point (x,y), with x and y both integers. For example, (2,3) is a lattice point but \left(4,\frac13\right) is not. In the diagram, how many lattice points lie on the perimeter of the triangle?

Image

Answer Choices
A. 16
B. 18
C. 20
D. 23
E. 30