Composing Shapes — Two Triangles Make a Square (Lois Ehlert's Color Zoo)

Read-aloud: Lois Ehlert's 'Color Zoo' (first 4 pages). Each animal is composed of layered geometric shapes — a tiger with triangle ears + circle eyes + rectangle face. Children identify shapes in each face.

• Show each page; pause for children to call out shape names
• Affirm: 'Each animal is BUILT from smaller shapes. Today we BUILD.'

Today we COMPOSE shapes — we put SMALL shapes together to MAKE BIG shapes. Watch. (Hold up two right triangles.) Two right triangles. If I put them together like this (assemble into a square), I make a SQUARE. (Hold up two squares.) Two squares — joined — make a RECTANGLE. (Hold up six small equilateral triangles.) Six triangles — joined like a flower — make a HEXAGON. (Demonstrate with pattern blocks.) Now look — and this is amazing — the SAME hexagon can be made in MANY ways: with 6 triangles, with 2 trapezoids, with 3 rhombuses. Same hexagon, different parts. This is called SUBSTITUTION.

• Six triangles = one hexagon.

  model Place 6 triangles on the hexagon outline; they tile it exactly.

  prompt Compose a hexagon with 6 triangles
• Two trapezoids ALSO equal one hexagon.

  model Place 2 trapezoids on the same hexagon outline.

  prompt Compose a hexagon with 2 trapezoids
• A house = a square + a triangle. Or you could say: a pentagon!

  model Square below, triangle (roof) on top.

  prompt Compose a 'house' with a square + a triangle on top

• How many triangles make a hexagon? (6.)
• What two shapes make a house? (square + triangle.)

M-K-S-GM-17-A Diagram

Three side-by-side hexagon outlines. Left: hexagon filled with 6 equilateral triangles in alternating green/blue. Middle: hexagon filled with 2 red trapezoids meeting at the center. Right: hexagon filled with 3 blue rhombuses meeting at the center. Caption: 'SAME hexagon — THREE compositions.' Style: clean diagrams, primary pattern-block colors.

• Hexagon Challenge: each child has a pre-printed hexagon outline + pattern blocks. Find at least 3 different ways to fill the hexagon (6 triangles; 2 trapezoids; 3 rhombuses; 1 trapezoid + 3 triangles; etc.).

  scaffold Pre-printed outline; reference card showing each completed way.
• Picture-builder: choose a target picture (house, tree, sailboat). Build it with foam shape pieces. Identify the shapes used.

  scaffold Pre-printed template outlines for each target picture.

M-K-S-GM-17-B Photograph

Top-down photo of a child's hands placing the 5th of 6 green equilateral triangle pattern blocks onto a printed hexagon outline. The 5 triangles are already in place; one space remains. Tray of remaining pattern blocks at the side (red trapezoids, blue rhombuses, orange squares, tan rhombuses, yellow hexagons). Style: documentary, natural classroom light.

• Build a hexagon. Tell me what shapes you used.
• Build a 'house' shape. What two shapes did you use?

• Math Detective close: 'Shapes can be BUILT from smaller shapes. Tomorrow we extend patterns!'

• Find a shape composition at home. Look at a window (rectangle made of smaller rectangles), a door (a rectangle), or a quilt (squares). Draw and label.