Using animals and people as the elements to count from one to one hundred, this book uses small numbers to first introduce the concept and then through repetition and building on that concept teaches how to reach much larger numbers. In relying upon the foundation of one through ten, with each number being represented by a cute creature, the reader is taught how to build math skills in a fun, inviting format.

The numbers are printed in a font size that is significantly larger than the text, cueing the reader to their importance. The use of multiple examples for the larger numbers also provides multiple avenues to understand how smaller groups are combined to form one larger group.This task continues to use the book One is a Snail, Ten is a Crab. It introduces students to the patterns of our place-value system and the significance of 10. The key understanding of unitising is introduced by asking students to represent teen numbers using one crab, which is the same as using 1 ten. In doing so, students move from using 10 ones to 1 ten.

This ingenious counting book is all about feet. Not the kind with inches. The kind with toes, or paws, or claws. “1 is a snail. 2 is a person. 3 is a person and a snail.” The four-footed dog plus a snail equals five. The eight –footed spider plus a snail equals nine. Ten? Why, ten is a crab! And that means 20 is two crabs. Forty is four crabs, or ten dogs or…you get the picture. And so will kids. No doubt they’ll be eagerly creating their own pedimentary equations in no time.” Prior to reading, warm up with some number recognition and partitioning questions. “Play Guess my Number” with the hundreds board by choosing a “mystery number” in your mind and having students ask questions to narrow the search for the mystery number (Does it have a 2 in the ones column? etc.). Reverse the game and give clues that help them narrow the search for another number (for example: My number has an even number in the tens column, or My number is 4 more than tidy number, or My number is made up of a two digits that are the same, etc.) have an understanding of the composition of numbers; for exampl, 7 can be made by combining 1 and 6.

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The humorous nature of the story is presented in multiple settings with crabs in a pyramid, crabs in a conga line, and crabs headed to the shore with their inner tubes. While they only have two small eyes and a simple mouth this provides ample expression as one crab is left behind with ten spiders, looking rather uncomfortable. In providing numerous ways to conceive of numbers, the text and the illustrations give the reader critical repetition. “”30 is three crabs…. or ten people and a crab.” This sequence begins with a focus on developing students’ counting skills to work with numbers beyond 10, then continues on to build early place value understanding as students investigate teen numbers. The key understanding of unitising is introduced as students use a group of 10 and some more ones to represent numbers 11 to 19. One is a snail, two is a person, three is a snail and a person, four is a dog, five is a dog and a snail!

Prior to this lesson you can have created copymasters of your own children’s drawings of the “units” (snail, person, dog, insect, crab) by asking someone to draw one of each and then reproducing them on a photocopier to create sheets of units or you can use the copymaster of clip art “units” or you can have each child do their own drawings for the activity.When you are counting by feet then 1 is a snail and 2 is a person and 4 is a dog! This book uses the number of feet on various animals to be the units by which numbers can be expressed. So for example: “40” can be 10 dogs (10 x 4) or 20 people (20 x 2) or 6 insects and a dog (6 x 6 + 4). The book is a humorous and colourful illustration of part-whole thinking.