Cogito
Grade 1 Math · Chapter 9 · Lesson 5
Shapes Inside Shapes
A shape you built can become a piece of something bigger.
10 problems · about 12 minutes · 1.G.A.2
What this lesson teaches
The child uses a composite shape as a piece in a larger composite shape, recognizing that pieces can themselves be built from pieces.
- A shape you build can be used as a piece.
- A rhombus is 2 triangles. A trapezoid is 3.
- Bigger pieces mean fewer pieces, not less shape.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
4 problemsReview — Making New Shapes: How many triangles fill one hexagon?
Answer 6
Why It takes 6 triangles.
Review — Naming Solid Shapes: A can of soup is shaped like what?
Answer A cylinder.
Why A can is a cylinder.
Review — Naming Flat Shapes: A shape has 6 straight sides. What is it?
Answer A hexagon.
Why 6 sides makes a hexagon.
Review — What Makes a Shape a Shape?: How many corners does a triangle have?
Answer 3
Why 3 sides make 3 corners.
Warm Up
Straightforward practice. Get the method working first.
3 problemsHow many triangles make one trapezoid?
Answer 3
Why A trapezoid is 3 triangles.
Can a piece be made of smaller pieces?
Answer Yes.
Why Shapes can hide inside other shapes.
How many triangles make one rhombus?
Answer 2
Why Look at the dotted line.
Build It Up
The same ideas with more to keep track of.
1 problemHow many triangles make one trapezoid?
Answer 3
Why Count the dotted pieces.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsHow many triangles are in 3 rhombuses?
Answer 6
Why 2 and 2 and 2.
Counting the Small Pieces: A trapezoid is 3 triangles. How many triangles are in 2 trapezoids?
Answer 6 triangles
Why 3 + 3 = 6 triangles, which is the whole hexagon.