Right Angles, Squares and Rectangles
Primary 1 · Mathematics
Right Angles, Squares and Rectangles
Lesson 4 of 5
12 min
Let's begin
Habimana puts his exercise book flat on the desk.
Two sides are long. Two sides are short. The corners look like door corners.
His book is not a square. So what is it? Today you will name it.
Look at the cover of your exercise book.
Check 1. It has 4 straight sides.
Check 2. The two long sides are the same length. The two short sides are the same length too.
Check 3. It has 4 right angles.
All three are true. The cover is a rectangle.
Sides that face each other are called opposite sides. In a rectangle, opposite sides match.
Cut string as long as the top side of your cover.
Hold it along the bottom side. The same length!
Now do the two short sides. They match each other too.
Push your book corner into all 4 corners. No gaps anywhere.
So the cover passes. It is a rectangle.
A door is a rectangle. It is tall and standing up.
A brick has a long thin face. That face is a rectangle too.
Umutoni says a thin one is not a rectangle. Test it with her.
All 4 corners are right angles. The opposite sides match.
So the thin one is a rectangle too.
Careful! Do not judge by how it looks. Check the corners. Check the opposite sides. If the checks pass, it is a rectangle.
Both shapes have 4 straight sides. Both have 4 right angles.
The sides tell them apart.
| Question | Square | Rectangle |
|---|---|---|
| How many sides? | 4 | 4 |
| How many right angles? | 4 | 4 |
| Are all 4 sides the same? | yes | no, two long and two short |
So ask one question: are all 4 sides the same length?
Yes means square. Two long and two short means rectangle.
4 sides. The sides facing each other match.
Sing the rectangle song with Akili and her friends.
Tip
Opposite sides match
Long with long. Short with short. All corners square.
Tall or thin does not matter. Only the checks matter.
Use your book corner and a piece of string. Then tap Show answer to check.
How many sides does a rectangle have?
Answer: 4. Two long ones and two short ones.
How many right angles does a rectangle have?
Answer: 4. Test every corner. No gaps.
A shape is tall and thin. It has 4 right angles and matching opposite sides. What is it?
Answer: a rectangle. Thin does not change the checks.
A shape has 4 right angles and all 4 sides the same length. What is it?
Answer: a square. All 4 sides match, not just the opposite ones.
Find a rectangle at home. Test its corners and its opposite sides.
Answer: a door, a mat and a window all pass the checks.
What you learned today
Quick check
In a rectangle, which sides match?
