Area of Shapes in the Plane
Primary 4 · Mathematics
Area of Shapes in the Plane
Lesson 2 of 5
25 min
Let's begin
Habimana helps his uncle lay square tiles on a new veranda. Each tile is exactly 30 cm on every side. "How much floor does one tile cover?" he asks.
A square is a special rectangle, so you already know most of what you need!
A square's length and width are the same. We call that length the side.
Area of a square = side × side
Example: Habimana's tile has sides of 30 cm. Area = 30 × 30 = 900 cm².
Example: a square vegetable plot has sides of 7 m. Area = 7 × 7 = 49 m².
The areas of squares with whole-number sides are the square numbers: 1, 4, 9, 16, 25, 36, 49, 64, 81, 100 … That is why they are called square numbers!
If you know the area, find the number that multiplies by itself to give it. A square field has an area of 64 m². Which number times itself is 64? 8 × 8 = 64, so each side is 8 m.
You can build squares in the Area Builder simulation too. Try 3 by 3, then 4 by 4, and watch how quickly the area grows.
Tip
Side times side. Double the side and the area becomes four times bigger: a 2 by 2 square is 4, a 4 by 4 square is 16.
Work each one in your exercise book first. Then tap Show answer to check.
Find the area of a square with sides of 5 cm.
Answer: 25 cm², because 5 × 5 = 25.
Find the area of a square room with sides of 6 m.
Answer: 36 m², because 6 × 6 = 36.
A square has an area of 49 cm². How long is each side?
Answer: 7 cm, because 7 × 7 = 49.
A square has a perimeter of 20 cm. Find its area.
Answer: 25 cm². Each side is 20 ÷ 4 = 5 cm, and 5 × 5 = 25.
Which is bigger: a square with sides of 9 m, or a rectangle 10 m by 8 m?
Answer: The square: 81 m² is bigger than 80 m².
What you learned today
Sources and credits
The stories, Rwandan examples, diagrams and practice questions were written by Ganzaa.
Quick check
What is the area of a square with sides of 8 cm?
