GoalCount the sides and vertices of plane shapes and name triangles, quadrilaterals, pentagons and hexagons.
New words
side · a straight line that makes the edge of a shapevertex · a corner where two sides meet (more than one: vertices)quadrilateral · any shape with 4 sidesplane shape · a flat shape you can draw on paper
Explanation
A plane shape is a flat shape. Its edges are called sides and its corners are called vertices. Count the sides by running your finger along each one, and mark where you start. A triangle has 3 sides and 3 vertices. A pentagon has 5 sides and 5 vertices. A hexagon has 6 sides and 6 vertices. For a flat shape with straight sides, the number of sides is always the same as the number of vertices. A shape with 4 sides is called a quadrilateral. The square, the rectangle, the trapezoid and the rhombus are all quadrilaterals.
Worked examples
This is a pentagon. Start at the marked corner and count: 5 sides and 5 vertices.
The hexagon is the shape of the cells in a honeycomb. It has 6 sides and 6 vertices.
These four shapes all have 4 sides and 4 vertices, so they are all quadrilaterals: the square, rectangle, trapezoid and rhombus.
Class activity
Shape hunt at home. Look for flat shapes around you: the face of a clock, a window, a sheet of paper, a tile, a road sign. For each one, count the sides and the vertices with your finger and say its name. Draw the three you like best in your notebook.
Practice
1
How many sides does this shape have?
6 sides. It is a hexagon.
2
How many vertices does a triangle have?
3 vertices.
3
Which shapes are quadrilaterals?
B and D (the square and the trapezoid). They have 4 sides.
4
A shape has 5 sides. How many vertices does it have? What is its name?
5 vertices. It is a pentagon.
5
Youssef counts the corners of this rectangle and says 3. Is he right?
No. A rectangle has 4 vertices. Youssef missed one, so he should mark where he starts.
