Composite shapes made from familiar shapes
A composite shape is made by putting familiar shapes together, such as squares, triangles, rectangles and semicircles. To describe one, look for the pieces. Count one kind at a time and tick each piece so none is missed. Shapes can be made from other shapes: two triangles can make a square. A rectangle that is 3 squares wide and 2 high is made of 2 rows of 3 squares, so it is covered by 6 squares.
Explore this idea with maths tools
Maths you can move
Build 8 + 5
Tap two gold counters to fill the ten-frame.
8 in the frame + 5 waiting. The total stays the same.
Words to know
- composite shape
- a shape made from two or more other shapes
- semicircle
- half of a circle
- piece
- one of the shapes that makes up the larger shape
Worked examples
A strip is made from triangles that are all the same size. There are 3 pointing up and 2 pointing down. How many triangles?
- 1.Count the ones pointing up: 3.
- 2.Count the ones pointing down: 2.
- 3.3 + 2 = 5.
= 5
A house has 3 squares and a triangle roof on 2 of them. A semicircle is on 1 more. How many shapes altogether?
- 1.Squares: 3. Triangles: 2. Semicircles: 1.
- 2.3 + 2 + 1 = 6.
= 6
A shape has 2 squares and 3 triangles. Each triangle is half a square. How many triangles would make the whole shape?
- 1.Each square is 2 triangles, so 2 squares are 4 triangles.
- 2.Add the 3 triangles: 4 + 3 = 7.
= 7
For parents
Method: Name each piece, then count one kind at a time and mark each as you count.
What to say: What shapes can you see inside? Which kind are we counting? Could two of these make a bigger shape?
Common mistakes:
- Counts more than was asked: all the pieces instead of one kind, or the empty grid spaces as well.
- Counts the squares, or only the whole squares, when the question is about triangles or all the shapes.
- Misses one piece when counting, usually one at the edge or a different shape or direction.
- Counts only some of the pieces, for example only the triangles pointing up, only the longest row, or only one dimension.
- Adds the width and height of a rectangle instead of multiplying to find how many squares cover it.