Shapes in the Plane
Primary 4 · Mathematics
Shapes in the Plane
Lesson 4 of 5
30 min
Let's begin
Keza's class is making a poster of shapes they can find at school. The door is a rectangle, a floor tile is a square, and the top of the teacher's desk is a rectangle too. Then Keza spots a kite shape in the pattern on a basket.
Some quadrilaterals are so common that they have their own names. Today you will learn how to tell them apart.
| Shape | Sides | Angles |
|---|---|---|
| Square | 4 equal sides; opposite sides parallel | 4 right angles |
| Rectangle | opposite sides equal and parallel | 4 right angles |
| Parallelogram | opposite sides equal and parallel | opposite angles equal |
| Rhombus | 4 equal sides; opposite sides parallel | opposite angles equal |
| Trapezium | one pair of parallel sides | (no special rule) |
| Kite | two pairs of equal sides that are next to each other | one pair of equal angles |
The small arrow marks show sides that are parallel. Tick marks show equal sides.
The diagonals help you tell the shapes apart too.
A square has 4 right angles, so it is a special rectangle. It has 4 equal sides, so it is also a special rhombus. And its opposite sides are parallel, so it is a parallelogram too!
Tip
Ask three questions: Are the sides equal? Are the angles right angles? Which sides are parallel? The answers tell you the shape's name.
Work each one in your exercise book first. Then tap Show answer to check.
A quadrilateral has 4 equal sides but no right angles. What is it?
Answer: A rhombus.
A quadrilateral has exactly one pair of parallel sides. What is it?
Answer: A trapezium.
Which two special quadrilaterals have diagonals that are equal in length?
Answer: The square and the rectangle.
Is every square a rectangle? Explain.
Answer: Yes. A square has 4 right angles and its opposite sides are equal, so it fits the rules for a rectangle.
A rectangle is 9 cm long and 4 cm wide. What is its perimeter?
Answer: 26 cm, because 9 + 4 + 9 + 4 = 26.
What you learned today
Sources and credits
The section on diagonals was written by Ganzaa. The stories, Rwandan examples, diagrams and practice questions were written by Ganzaa.
Quick check
A quadrilateral has 4 right angles, but its sides are not all equal. What is it?
