I’ll hopefully be able to turn the last problem into fun Zometool project, but for today I thought it would be neat to talk through two of the problems with my kids.

I chose the problem about brothers and sisters for my 4th grade son. He did a nice job with it and managed to work his way to the end:

After he finished, we talked about one point that confused him a little bit:

For my 6th grade son I chose the problem about escalators. He had an approach that was a little different from what I was expecting:

When he finished we also reviewed his solution and talked (in a pretty haphazard way, sorry!) about a slightly different approach:

I especially liked the escalator problem because it reminded me of one of my all time favorite math contest problems – Problem 10 from the 1987 AIME:

The escalator question relates to two other stories that might interest your kids:

(1) Terry Tao question about where to tie your shoes in an airport

(2) Steven Landsburg’s marginal confusion about marginal decisions