Jim Prop's gam: Swine in a Line:
From a given starting position is there a move you can make so you'll always win? There is a followup video.
Brenford's law(first digits are mostly ones (logarithmic) Easy to collect data and observe. See: https://en.wikipedia.org/wiki/Benford%27s_law
Problem Stream using the Trivial Inequality(Great for Whiteboard).
Start with the Trivial Inequality
Prove the AM-GM inequality as a demo.
Unit Fractions in Tessellations:
If you draw lines from the corners of a square to the centre of each edge, you can make rhombuses of area 1/5, 1/4, 1/3 pic.twitter.com/Cm9bGq82t6— David Butler (@DavidKButlerUoA) June 23, 2017