# Multiplication Explorers, the book

Natural Math was one of the first web pages in the world about multiplication, circa 1996. We were the first in the world to offer open online courses for parents in the early 2000s. Our most popular, longest running course is about multiplication as the cornerstone of algebra and calculus. Our quick, powerful pattern-based method of learning the times tables and our creative art activities have been tested by thousands of families, math clubs, and classes. We’ve adapted advanced, beautiful math to make it kind and radically accessible. “You should write a book,” people would say.

We wrote the book!

(A mini-poster from one of our courses.)

# A Powerful Method to Learn Times Tables – Now a Book

Based on our longest-running, most popular online course, this book features
• Pattern-based approach to learning times tables
• Engaging activities that explore the beauty of algebraic and calculus reasoning
• Radical accessibility – anyone from 3 to 103 years old can enjoy the book’s projects
• A kind and thoughtful path to advanced mathematics

### Ancient merchants’ finger trick from Chapter 3, “Times Tables”

This amazing trick was first recorded around 15th century. Back then, merchants used finger reckoning to calculate prices and profits. A calculating device took half a room, while finger math was easy to take on a trip. Merchants twiddled their fingers away from the prying eyes of their competitors: that’s where the phrase “under the table” came from. Try this for a party trick, or to check your memory of the hardest multiplication facts. Once you practice enough, you can do the trick like a merchant of old, under the table.

Does the trick always work? Even a young child can prove that it does. Check every multiplication fact from 6 x 6 to 10 x 10, and the answer will come true. But that proof is not very satisfying.

How about formal algebra? Click to read a formal algebraic proof. During the crowdfunding campaign for the book, we’ll be collecting and sharing various joyful proofs.