# Investigate the relationship between features of circles such as circumference, area, radius and diameter. Use formulas to solve problems involving circumference and area (ACMMG197)

**LO:To investigate the features of circles such as circumference, area, radius and diameter.
**

**Know:**

- the properties and features of circles

**Understand:**

- That formulas can be used to quickly find the features (area and circumference) of a circle.

**Do:**

- I can find features of a circle.

# Features of Circles

**Diameter of a Circle**

A **diameter** of a circle is the **distance from one side of a circle to the other side of a circle.** It splits a circle into 2 **equal** pieces.

**Radius of a Circle**

A **radius** of a circle is the **distance from the center of the circle to the edge**.

**Circumference of a Circle**

**Circumference** is the **perimeter of a circle** or the distance around the outside of the circle

# Formulas for Finding Features of Circles

**Formula for finding the Circumference of a circle. **

There are **2 formulas** for finding the circumference of a circle, they both work out to give you the same answer:

**C = ∏ x d**

** Circumference = Pi x diameter**

**C = 2 x ∏ x r**

** Circumference = Pi x radius**

**Area of a Circle**

Area of a circle is the **amount of space** that the **inside** of the circle occupies.

**Formula for finding the area of a circle:**

**A = ∏ x r x r**

** Area = Pi x r (squared)**

# Features of Circles Videos

**Circle Quiz**

**Circle Quiz**

What is the area of a circle with a radius of 8 cm?

- About 200 cm squared
- About 2000 cm squared
- About 50 cm squared

**What is the circumference of a circle with a radius of 10 cm?
**

- About 300 cm
- About 20 cm
- About 60 cm

**What is the name of the perimeter of a circle?**

- Pi
- Circumference
- Diameter

**A line that cuts a circle perfectly into two equal pieces is called the?**

- Diameter
- Radius
- Circumference

**If the diameter of a circle is 10 cm, then the radius must be?**

- 5 cm
- 20 cm
- 10 cm

**Grade Me**