There are two sets of numbers. The second is the result of the first after an increase by a constant percentage. How can you find that percentage if one set of numbers is in code?

What's the most efficient proportion for a 1 litre tin of paint?

What angle is needed for a ball to do a circuit of the billiard table and then pass through its original position?

A finite area inside and infinite skin! You can paint the interior of this fractal with a small tin of paint but you could never get enough paint to paint the edge.

What is the total area of the triangles remaining in the nth stage of constructing a Sierpinski Triangle? Work out the dimension of this fractal.

Make a poster using equilateral triangles with sides 27, 9, 3 and 1 units assembled as stage 3 of the Von Koch fractal. Investigate areas & lengths when you repeat a process infinitely often.

Some excellent use of algebraic interpretation by Joan, Jia and Jeremy in the Inside Outside problem.

The harmonic triangle is built from fractions with unit numerators using a rule very similar to Pascal's triangle.