Online Geometry Problem 787: Right Triangle, Inradius, 18 Equal Circles,
Line Tangent, Legs, Hypotenuse, Ratio, Metric Relations. Level: High School,
SAT Prep, College,
Mathematics Education

The figure below shows a right triangle ABC with
inradius x and 18 equal tangent circles of radius r, so that leg AB is tangent
to 6 circles, BC is tangent to 13 circles and AC is tangent to 2
circles. Prove that x = 5.r