In this introduction to polygons, a triangle convinces a shapeshifter to make him a quadrilateral and later a pentagon, but discovers that where angles and sides are concerned, more isn't always better.

שם הספר
This book is about time
Brown Paper School book: Math for Smarty Pants
Greedy Triangle (Scholastic Bookshelf)
Spaghetti And Meatballs For All! (Scholastic Bookshelf: Math Skills)