Maths Olympiad Prep

Library / /107 of 860

Geometry Difficulty 4.8 AIME Find the answer

How many lattice points are enclosed by the triangle with vertices (0,99),(5,100)(0,99),(5,100), and (2003,500)?(2003,500) ? Don't count boundary points.

A number or a short expression. Spacing and $ signs are ignored.

Solution

Using the determinant formula, we get that the area of the triangle is 512003401/2=1\left|\begin{array}{cc} 5 & 1 \\ 2003 & 401 \end{array}\right| / 2=1 There are 4 lattice points on the boundary of the triangle (the three vertices and (1004,300)(1004,300) ), so it follows from Pick's Theorem that there are 0 in the interior.

Want a route through all this instead of an archive? The track puts 2,000 problems in a working order, from AMC 10 level to the IMO shortlist.

Source: Omni-MATH, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.