Area and Land Measurements
Primary 4 · Mathematics
Area and Land Measurements
Lesson 2 of 5
20 min
Let's begin
Habimana's school wants to plant grass on a rectangle of ground in front of the office. It is 8 m long and 5 m wide. The gardener sells grass by the square metre.
Must they draw 1 m squares on the ground and count them one by one? No! There is a faster way. Today you will find it.
Draw the rectangle and split it into 1 m squares.
There are 5 rows, and each row has 8 squares. Instead of counting all 40 squares, multiply: 8 × 5 = 40. The area is 40 m².
Worked example 1
A classroom floor is 9 m long and 7 m wide. What is its area?
Area = 9 × 7 = 63 m².
Worked example 2
A book cover is 21 cm long and 15 cm wide. Area = 21 × 15 = 315 cm².
A square has four equal sides, so its length and width are the same.
Worked example 3
A square vegetable garden has sides of 6 m. Area = 6 × 6 = 36 m².
Worked example 4
A rectangular plot has an area of 48 m². Its width is 6 m. How long is it?
Length × 6 = 48, so length = 48 ÷ 6 = 8 m. Check: 8 × 6 = 48.
Careful! Area and perimeter are different. The 8 m by 5 m grass patch has a perimeter of 8 + 5 + 8 + 5 = 26 m, but an area of 40 m². Both sides must also be in the same unit before you multiply.
Try the Game screen of the Area Builder simulation. Build rectangles with a given area, and check your answers.
Tip
Rows times columns. Length × width counts every square at once. For a square it is side × side. Write the answer in square units: cm² or m².
Work each one in your exercise book first. Then tap Show answer to check.
Find the area of a rectangle 7 m long and 4 m wide.
Answer: 28 m², because 7 × 4 = 28.
Find the area of a square with sides of 9 cm.
Answer: 81 cm², because 9 × 9 = 81.
A sleeping mat is 3 m long and 2 m wide. What is its area?
Answer: 6 m².
A rectangle has an area of 56 m² and a length of 8 m. How wide is it?
Answer: 7 m, because 56 ÷ 8 = 7.
A school garden is 12 m long and 10 m wide. Seeds for 1 m² cost 150 Frw. How much do seeds for the whole garden cost?
Answer: The area is 12 × 10 = 120 m². The seeds cost 120 × 150 = 18 000 Frw.
What you learned today
Sources and credits
The stories, Rwandan examples, drawings and practice questions were written by Ganzaa.
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