Thanks _ttg for posting this! I just spent an hour with my 5-year old going over all the functions mentioned in the post and then some. I would give him an 'x' and he returned f(x) to me. Eventually we ended up at Collatz Conjecture and he absolutely loved it. I've always wanted to explain that one to him but it was hard to simplify the concept. Starting with simpler f(x) and building up to comparisons like min/max worked out perfectly. He completed the entire chain of 7 on his own! Thank you :)