MathDB
maximum circles

Source: Greek MO 2007

March 5, 2007

Problem Statement

In a circular ring with radii 11r11r and 9r9r, we put circles of radius rr which are tangent to the boundary circles and do not overlap. Determine the maximum number of circles that can be put this way. (You may use that 9.94<99<9.959.94<\sqrt{99}<9.95)