Planning tool

Students:

• identify and name the parts of a circle, including circumference, diameter and radius 
• understand the significance and meaning of the symbol π as the ratio between the circumference and diameter of a circle
• know and use the relationships between the radius, diameter and circumference
• use a formula to find the area of a circle or sector
• use a formula to find the perimeter of a sector.

Some students may:

• confuse radius and diameter. Be explicit about using correct vocabulary. Have a list of common terms displayed to assist students.
• not appreciate that π is a number.
• use the wrong measurement. Support students to identify the diameter and radius of each circle and which measurement is required to solve particular problems.
• confuse square numbers – students often multiply by two instead of multiplying the number by itself.
• have difficulty in leaving answers in terms of π, preferring rounded decimals. Note: suggesting students always use 3.14 to represent π may lead students to think that π = 3.14.
• see π as a variable and they substitute 3.14 for that variable.
• have difficulty in relating circumference to the distance around a circle. Make explicit that the circumference is another word for perimeter.
• confuse the circumference and area formulas.

The Learning from home activities are designed to be used flexibly by teachers, parents and carers, as well as the students themselves. They can be used in a number of ways including to consolidate and extend learning done at school or for home schooling.

Learning intention

• We are learning to identify the features of a circle such as circumference, radius and diameter.
• We will apply the formula to calculate the circumference of a circle.

Why are we learning about this?

It is important to build understanding and knowledge of the correct formula for measuring circles and how it links to other areas of the curriculum. In the real world, curves, cylinders, spheres and circles are all around us. Whether it's the boundary of a go-kart track or the gears that make up the engine in a car, measuring curves allows us to plan, design and build the world around us. 

What to do

Task 1:

• Open the following link: Measurement and geometry – Features of circles.
• Use section 1 to learn about the features of a circle and how to find the circumference and area. Record key information that you found useful. Don't worry if you see that it is Year 8 content. That's OK. This content has moved to Year 7 and is still relevant and worded clearly.
• Move through sections 2, 3, 4 and 5. Answer the questions in your workbook.

Task 2: 

• Find three circular shapes around your home; these could include a round table, a bike wheel or a circular mat.
• Use a piece of string to measure the circumference of each shape. Next, measure the diameter of each.
• Create a table in your book and record your answers.

1. What do you notice about the results for C/d?
2. Explain what is occurring and give reasons for this.
3. What do you think would be the circumference of a circle that has a diameter of 30 cm?

Success criteria

• I can apply the formula for the circumference of a circle.
• I can understand and utilise π.
• I can identify and name parts of a circle.
• I can use circle formulas to solve problems.