Lesson Notes By Weeks and Term v5 - Grade 3
Measurement: perimeter, area (counting squares) and volume (intro) – Week 5 focus
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Measurement: perimeter, area (counting squares) and volume (intro) – Week 5 focus
Download the Lessonotes Mobile South Africa app for faster lesson access on Android and iPhone.
Subject: Mathematics
Class: Grade 3
Term: 3rd Term
Week: 5
Theme: General lesson support
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This week, we're diving into the world of measurement! We'll be exploring perimeter, area, and getting a sneak peek at volume. Understanding measurement is super important. Imagine you're helping your family build a vegetable garden. You need to know how much fence to buy (perimeter), how much soil to use (area), and even how much water the watering can holds (volume)! These skills help us in everyday life, from cooking to building to playing.
Perimeter: Perimeter is the distance around a shape. Think of it like walking around the edge of your school's netball court. To find the perimeter, we add up the lengths of all the sides of the shape. We always measure perimeter in units of length, like centimetres (cm), metres (m), or even paces! Why do we need to know perimeter? Imagine you are helping your Gogo put up a fence around her garden to keep the chickens out. You need to know the perimeter to buy the right amount of fencing.
Example 1: A rectangular garden is 5 metres long and 3 metres wide. What is the perimeter of the garden?
Solution: Rectangle has two lengths and two widths. Perimeter = Length + Width + Length + Width Perimeter = 5m + 3m + 5m + 3m Perimeter = 16m Example 2: A square has sides of 4 cm each. What is the perimeter of the square?
Solution: Square has 4 equal sides. Perimeter = Side + Side + Side + Side Perimeter = 4cm + 4cm + 4cm + 4cm Perimeter = 16cm Area: Area is the amount of surface a shape covers. Think of it as the amount of space inside your classroom. We measure area in square units, like square centimetres (cm²) or square metres (m²). Today, we will find the area by counting squares. Why do we need to know area? Imagine you are helping your parents tile the floor of your bathroom. You need to know the area to buy the right number of tiles.
Example 3: A rectangle is drawn on a grid. It is 4 squares long and 3 squares wide. What is the area of the rectangle?
Solution: We can count each square inside the rectangle. Alternatively, we can multiply the number of squares in length and width. Area = Length x Width Area = 4 squares x 3 squares Area = 12 square units Example 4: A shape is made up of 7 squares. What is its area?
Solution: Each square represents one unit of area, therefore the total area is 7 square units.
Introduction to Volume: Volume is the amount of space something takes up. Think of it as how much water fits inside a bottle. We can measure volume by counting how many smaller containers (like cups) it takes to fill a larger container (like a jug). We're just starting with this, so we'll use simple counting! Why do we need to know volume? Imagine you are helping your family cook pap. You need to know the volume of water to add to the maize meal.
Example 5: How many cups of water do you need to fill a 2-litre bottle? (This would be a practical demonstration done by teacher).
Solution: We fill cups of water into the bottle and count how many cups fill the bottle. The number of cups is the volume.
Important Difference: Perimeter is the distance around a shape (like a fence). Area is the space inside a shape (like the floor). Volume is the space that an object occupies. Guided Practice (With Solutions)
Question 1: A triangle has sides of 6cm, 8cm, and 10cm. What is its perimeter?
Solution: Perimeter = 6cm + 8cm + 10cm = 24cm. The key here is to add all the sides together.
Question 2: A rectangle is drawn on a grid. It is 5 squares long and 2 squares wide. What is the area of the rectangle?
Solution: We can count squares. Alternatively, Area = Length x Width = 5 squares x 2 squares = 10 square units. We can see the area as covering a number of smaller squares.
Question 3: You have a bucket. You use a cup to fill it. You need 8 cups of water to fill the bucket. What is the volume of the bucket in cups?
Solution: The volume of the bucket is 8 cups. The volume is represented by how many cups filled the bucket.
Question 4: Thabo is building a square sandpit. Each side of the sandpit is 2 meters long. What is the perimeter of the sandpit?
Solution: A square has 4 equal sides.
Therefore, Perimeter = 2m + 2m + 2m + 2m = 8m. Or, Perimeter = 4 x 2m = 8m.
Question 5: Fatima draws a shape on grid paper. When she counts the squares inside the shape, she counts 15 squares. What is the area of the shape?
Solution: The area of the shape is 15 square units. Each square on the grid represents one unit of area. Independent Practice (Questions Only) A rectangular picture frame is 20 cm long and 15 cm wide. What is the perimeter of the picture frame? A square tile has sides of 10 cm. What is the perimeter of the tile? A shape on grid paper is 6 squares long and 4 squares wide. What is the area of the shape? A shape is made up of 11 squares. What is its area? You use a small glass to fill a water bottle. You need 5 glasses of water to fill the bottle. What is the volume of the bottle in glasses? Sarah wants to put a ribbon around a square birthday cake. Each side of the cake is 30cm. How much ribbon does she need? John's bedroom is rectangular. It is 4 metres long and 3 metres wide. What is the perimeter of John's bedroom? Lebo built a shape with blocks on a table. The shape takes up 20 squares on the table. What is the area of the shape? Imagine a small bowl. You use a spoon to fill the bowl with sugar. It takes 6 spoons of sugar to fill the bowl. What is the volume of the bowl in spoons?