From the Manufacturer:
When does less equal more? When using Math Gear to learn subtraction! Turn mastering math facts into hands-on fun! More portable than a book and more practical than flashcards, the pocket-sized, 14-page Math Gear is a sturdy, interactive teaching tool with a fun, gadget-like look and feel. Turn the wheel for a math problem, solve it, then lift the flaps to check the answer! Math Gear also includes fun facts about numbers and math. This book (also available for addition, multiplication, and division), makes it fun and easy for kids four and older to learn and practice subtraction facts, anywhere, anytime!