Jonathan Y.

Mr. Moves’ class decided to have a chess tournament. If each of the 10 children played each other’s once, how many games were played?

This is one of those products that some of us just have to memorize. It's too big to do on fingers... But the answer has two digits in sequential order! :)

In one week, the pumpkin vines grow 3 cms. Today the vines are 20cms long. How long were the vines two weeks ago?