An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.

A circle is inscribed in an equilateral triangle. Smaller circles touch it and the sides of the triangle, the process continuing indefinitely. What is the sum of the areas of all the circles?

Rectangle PQRS has X and Y on the edges. Triangles PQY, YRX and XSP have equal areas. Prove X and Y divide the sides of PQRS in the golden ratio.

Two murders take $2x$ hours, $6$ car thefts: $6 \times \frac{x}{6}$, 4 bank robberies: $4 \times \frac{x}{2}$

Total = $2x + 2x + x = 5x$.

This problem is taken from the UKMT Mathematical Challenges.