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One is a Snail Ten is a Crab

Updated: Oct 16

Literature-Launched Lessons for Grades K-3

One is a Snail Ten is a Crab by April Pulley Sayre and Jeff Sayre is a children’s book all about feet, and it’s my current favorite. Did you know that a snail has one foot? Snails are unipeds, part of the Gastropod family, and they use their foot to push away sediment as they crawl. There’s a lot of science in this book. But there’s also a lot of math too!

Humans have two feet, dogs four, insects six, spiders eight, and crabs have ten feet! Three is a human and a snail. Ten is a spider and two snails. Thirty is three crabs or ten people and a crab. And so on and so on. Numbers can be decomposed into endless combinations of animals and the number of feet that they have, and this makes for some terrific math explorations, all from reading One is a Snail Ten is a Crab.

Teachers can use the book in kindergarten to help students learn about unitizing and teen numbers, they can use it to teach number decomposition and addition within 100 or 1000 in first and second grade, and third grade teachers can use the book as a context for teaching multiplication. Whichever grade level you teach, One is a Snail Ten is a Crab is a great resource to connect mathematics to the world around us. I recently used it as a springboard for a math lesson in Lila Murphy’s second grade class in San Diego.

Launching the Lesson

To quickly grab students’ attention, I showed the class a chart I’d made (see below) and asked, “How many feet does each animal have? What else do you notice?” The chart gave them a chance to tap their prior knowledge and experience, and it was also a nice way to introduce them to the book. I gave them some time to think and then had them talk with a partner.

As I circulated and listened to their conversations, I noticed that many students were fascinated and surprised by the information on the chart. They happily chatted away, some making personal connections to their pet dogs and cats, and others relating stories about trips to the beach and the zoo.

Next, I read the book aloud to the class (One is a Snail) asking questions along the way such as,

“What do the authors mean when they say 7 is an insect and a snail?”

“Why is 30 a crab and ten people?”

“Why is 50 ten dogs and a crab?”

“What combination of animals could make 100?”

These questions gave Lila’s students an opportunity to think about how numbers can be composed and decomposed in different ways and connect quantities to things in the world.

Providing a Model

After reading the book, I told the students that they’d each make a page for a class book based on One is a Snail Ten is a Crab. To provide an example of what a page might look like, I elicited a few ideas from students. Using a document camera, Lila carefully sketched the six dogs and four insects that the students suggested. When she was finished, we had the class figure the animals’ total number of feet (48).

“So, 48 is six dogs and four insects,” I said as Lila recorded the sentence next to the drawings. “What equation can we write that would match the sentence (or story) and the drawings?” Students suggested a few equations that would represent Lila’s drawings: 4+4+4+4+4+4+6+6+6+6 = 48 or, 24 + 24 =48. Some noticed that the result was the same for the two different equations, but the addends were different.

Making a Class Book

Students enjoyed making their own page for our class book. Below are a few examples.

“18 is 4 dogs 2 snails.”

“32 is 2 dogs and 3 spiders.”

“16 is 3 dogs and 4 snails.”

Summarizing the Lesson with a Guessing Game

Once students finished their book pages, we called them back to the rug. To summarize the lesson, Lila wrote 18 Feet on the board.

She then asked, “What animals could make 18 feet? And what equations would describe them?”

After a brief partner talk, Lila elicited the following ideas from her class which she posted on the board:

1 crab + 1 spider = 18 feet


1 crab + 8 snails = 18 feet


1 crab + 2 dogs = 18 feet


1 crab + 4 humans = 18 feet


2 insects + 1 dog + 1 human = 18 feet

6+6+4+2 = 18

Reflecting on the Lesson with Lila

After the lesson, I followed Lila as she led the students outside for recess. As we watched the children play, I asked what were her big takeaways from the lesson.

“Well, the kids for sure were engaged and enjoyed doing the math and connecting math to animals and their feet. And they seemed to be able to combine animals’ feet into one number (12 can stand for 6 feet plus 6 feet).

“I liked that the lesson helped students see that numbers stand for quantities in real life, not just things we add together randomly without a purpose. And that we can take numbers apart and put them back together.”

“Finally, I liked the lesson because it is naturally differentiated, it had a low floor and high ceiling. Students could get real fancy and complicated with their stories and equations, or not. Everyone could participate and be successful in some way.”

Lesson Plans for Grades K-3

Counting, unitizing (seeing and counting numbers in groups rather than as individual units) and number decomposition and composition (taking numbers apart and putting them back together) are important ideas that are crucial for children’s success with place value and multiplication. One is a Snail Ten is a Crab is a wonderful book that can lead to activities that develop these important ideas and connect mathematics to the world around us. To access lesson plans for kindergarten, first/second and third grades, use the links below and have fun!

Lesson Plan for Kindergarten.docx
Download PDF • 452KB

One is a Snail Ten is a Crab 1_2 grade.docx
Download PDF • 489KB

One is a Snail Ten is a Crab 3rd grade.docx
Download PDF • 332KB

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