Illustrative Mathematics Kindergarten, Unit 3: Flat and Solid Shapes
In this unit, your child looks closely at shapes. Kindergartners name and describe flat shapes like triangles and hexagons and solid shapes like cones and cubes, notice that a shape keeps its name when it is turned, count sides and corners, and build shapes from sticks or clay. Counting from the numbers-to-10 unit shows up here too, ahead of the next unit on adding and subtracting.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
What is my child learning in Unit 3?
- Describing shapes they find at school and at home, and using words like above, behind, and next to for where things are. Learn more: Spotting shapes and saying where things are
- Noticing that a shape keeps its name when it is turned, flipped, or made bigger or smaller. Learn more: Naming shapes turned any which way
- Sorting shapes as flat, which means two-dimensional, or solid, which means three-dimensional, such as a square and a cube. Learn more: Telling flat shapes from solid shapes
- Counting sides and corners to describe and compare shapes, and naming how a triangle and a hexagon differ. Learn more: Comparing shapes by their sides and corners
- Building shapes from sticks and clay balls and drawing shapes they see, with straight sides that join. Learn more: Building and drawing shapes
Sample questions to try together
These are real questions from our practice. Tap the speaker to hear one read aloud, or the light bulb for a hint, and talk about the answer together.
Question 1 of 3
What shape is a slice of pizza?
- Triangle
- Circle
- Square
How you can help
- Build shapes with straws or craft sticks and play dough corners, and ask your child to count the sides and corners of each one.
- Turn a paper triangle around on the table and ask your child after each turn whether it is still a triangle.
- Find a solid shape at home, like a box, and a flat shape, like a drawing of a square, and talk about how they are different.
Where kids can get stuck
- Insisting a triangle pointing down is not a triangle, because it looks different from usual.
- Calling a ball a circle because it looks round from the side, using a flat name for a solid shape.
- Building a shape with sides that do not meet, leaving a gap at one corner.
Practice makes perfect
Bobby's Math Club has practice problems that adapt to your child’s level, each with a detailed explanation and an easy-to-follow video, so your child can build confidence in these skills one step at a time.
Words your child will hear
- two-dimensional
- Flat, like a shape drawn on paper; also called 2D.
- three-dimensional
- Solid, like a block you can hold; also called 3D.
- triangle
- A flat shape with 3 straight sides and 3 corners.
- hexagon
- A flat shape with 6 straight sides and 6 corners.
- cone
- A solid shape with a round, flat bottom and a point at the top.
- cube
- A solid shape with 6 square faces, like a block.
- side
- A straight line that makes part of a flat shape's edge.
- corner
- The point where two sides of a shape meet.
Ready to build your child’s confidence with naming and building shapes?
In Bobby's Math Club, your child practices these skills at just the right level, with a hint when they need one, a clear explanation after every question, and kid-friendly videos. Unlimited practice is free.
Join the club
Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.
Which math standards does Illustrative Mathematics Kindergarten Unit 3 cover?
Illustrative Mathematics Kindergarten Unit 3 covers these math standards. Each one links to what it means, sample questions, and teaching strategies.
For teachers: Unit names and order vary between editions and districts, so your school’s own materials have the exact sequence. Learn how Bobby's Math Club can help your students grow.