1. Anytime there’s a “guess how many are in the jar” contest, I get my kids to use the appropriate formula for volume to see if they can guess the right answer. They usually get really close.
2. Show them how math helps them win at games. Monopoly is great for this where you can calculate the ROI for different properties on the board, how many houses are ideal, etc. you can go further with likelihood of landing on certain properties too.
It works. The hardest thing about math motivation as a kid is “where will I use this?”
Moneyball (movie) is a good one too.