Some good puzzles here
A link on another blog, I think provided by Chris at http://chrisfmathsphysicsmusic.blogspot.com/, took me to here: http://www.maths.cam.ac.uk/undergrad/nst-pastpapers/2011/index.html whereupon, of course, I had to have a look at the papers on offer.
Within Part IA Paper 1 lies this funny 2 mark question, which can be solved with GCSE higher level maths: A circle is inscribed within an equilateral triangle. Find the ratio of the circle to the ratio of the triangle (Q5 here: http://www.maths.cam.ac.uk/undergrad/nst-pastpapers/2011/PaperNST_IA_1.pdf)
By the mark scheme, it should take three minutes. How quickly can you do it?