Gray is apprehensive about her first day at her new school, until she meets PI, a tiny math guru who assures her that she will meet and befriend other mathematically precocious students like herself. Mrs. Googol-Plex’s classroom is a magical place where Gray, Alex, and friends learn simple and surprising new ways to understand subtraction.

Because the characters in the story learn about subtraction primarily through the use of money, this book comes with a packet of fake money that students can use to practice with.