MathDB
colored lines x = k, y = m, 19x+96y= c

Source: II Soros Olympiad 1995-96 R3 9.4 https://artofproblemsolving.com/community/c2416727_soros_olympiad_in_mathematics

June 4, 2024
combinatoricscombinatorial geometryColoring

Problem Statement

All possible vertical lines x=kx = k and horizontal lines y=my = m are drawn on the coordinate plane, where kk and mm are integers. Let's imagine that all these straight lines are black. A red straight line is also drawn, the equation of which is 19x+96y=c19x+96y= c. Let us denote by MM the number of segments of different lengths formed on the red line when intersecting with the black ones.(The ends of each segment are the intersection points of the red and black lines. There are no such intersection points inside the segment.) What values can MM take when cc changes?