Tuesday Teacher Tips: How Does 1 + 1 = 5?

Welcome to the Tuesday Teacher Tips series! Each week we’ll highlight teaching and learning resources, ideas to use in the classroom, as well as things to ponder as you go about your teaching day.

An author and illustrator I admired a lot, David LaRochelle, recently came out with a new book, 1 + 1 = 5: and Other Unlikely Additions. David, a former elementary teacher, has visited my previous school many times as a writer-in-residence and I’ve always loved his easy, imaginative way of teaching. That seemingly effortless way of leading kids into learning has translated into his latest book.

I recently read his new book to my third graders. When I showed them the cover and read the title, immediately students erupted: “What?” “That’s wrong!” “They made a mistake!” My only response was, “Well, let’s see.” And then I started to read.

1 + 1 = 5?
1 set of triplets + 1 set of twins = 5 babies!

A few kids understood and murmured, “Oh!”

1 + 1 = 14?
1 ant + 1 spider = 14 legs!

A few more kids got it. It didn’t take long before everyone was trying to guess what 1 + 1 would equal in the next equation.

This was a true, interactive book. The strange equations are presented first, accompanied by a few visual clues that are hidden within the picture. Then you turn the page to find out the answer, in both words and illustrations.

On  the home page of David’s website, look under Two New Books! and click on “free teaching materials.” You’ll be able to download a host of great material to use with your class to go along with this book.

Using one of the suggestions in the teacher’s guide with my own class, I had my students make up their own equations and write them on a folded piece of construction paper with the equation on the front and the answer inside. One suggestion on this activity, do a lot of brainstorming of things that come in sets (1 cat has four legs, 1 insect has six legs), otherwise you’ll get some very random equations.

I interviewed David, and asked him a few questions about writing this book.

LISA: What was your inspiration for 1+1=5? What drew you to writing a book about math?

DAVID: The book began with a list of odd equations that I jotted down on a legal pad:
1 + 1 = 5: 1 bike + 1 trike = 5 wheels
1 + 1 = 7: 1 square + 1 triangle = 7 sides, etc.
I thought the equations were fun, but I didn’t know what I could do with them. Many months later I ran across the legal pad again and thought perhaps I could illustrate them, put them together in a book, and send them to an editor. I was delighted when an editor at Sterling was interested. She eventually chose someone else to be the illustrator, but I’m excited that she wanted to publish them at all!

LISA: How did you come up with the equations for the book?

DAVID: I did a lot of brainstorming. The first equations were easy, but I wanted each 1 + 1 equation to have a different answer. There are many ways to add two things together to get eight (1 chair + 1 table = 8 legs, 1 dog + 1 cat = 8 feet, 1 skateboard + 1 wheelchair = 8 wheels) but I only included one. I also wanted each equation to be about things that children could relate to (animals, sports, etc.).

LISA: In the teacher resource pages [on your website] it says that you had over 150 subtitles for the book. How many different equations did you have for the book? How did you decide which ones to use?

DAVID: I brainstormed lots of equations that were either too complicated (1 hour + 1 minute = 3,660 seconds) or too imprecise (1 star + 1 snowflake = 11 points). I picked my favorite 15 to send the editor, but she had me replace almost a fourth of them. Her main concern was that if the book were translated into a foreign language, the equations needed to make sense in different countries. For example, I had to replace 1 dime + 1 nickel = 15 cents because of the different currencies used in foreign cultures. Likewise we couldn’t think of a way to illustrate 1 October + 1 November = 61 days without relying on holidays or seasons that might not be universal across the globe.