# Step 8

Know and use the formulae for the area and circumference of a circle

## Probing questions

• What is the minimum information you need to be able to find the circumference and area of a circle?
• Give pupils some work that includes mistakes.
• Ask them to identify and correct the mistakes.
• How would you go about finding the area of a circle if you knew the circumference?

## What if pupils find this a barrier?

Ensure that pupils understand that $\mathrm{\Pi }$ is the ratio of the length of the circumference of a circle to its diameter.

Demonstrate an approximation to the area by cutting a circle into 16 sectors and forming an approximation to a rectangle to establish a visual approximation to $\pi {r}^{2}$.

Ensure that $\pi {r}^{2}$ is seen as $\pi ×r×r$.

Give pupils some work that includes mistakes and ask them to correct them. Be specific about common mistakes.