Quelle est la bonne boîte?

The mathematical word featured in this episode is: length. The Math-Monster Squad receives a desperate call from the All-Grumpy Monster who is crumbling under orders for ice cream slime cubes, and they can't seem to find boxes of the right length to wrap them. Watching the All-Grumpy Monster, the math monsters find that he randomly chooses boxes that are either too long or too short to hold the amount of frozen slime cubes for each of his orders. With the help of a Teletou-monster, they learn to make a ruler with numbered empty containers and this allows them to find the boxes of the correct length for each amount of ice slime cubes.