Real World Math: Exploratory Lessons - Four Color Map
Real World Math

This is a fairly simple puzzle for students to solve but it took over a century for it to be proven with computers. 

Real World Math: Exploratory Lessons - The Flat Earth
Real World Math

The Spherical Geometry exercises included here will cover what some may consider Non-Euclidean Geometry or Differential Geometry. 

Real World Math: Exploratory Lessons - Network Theory
Real World Math

Network Theory investigations deal with how paths can be drawn in a continuous circuit.