Area of a circle | Maths | Quizalize & Oak National Academy

Starter quiz

The ______ is any line segment that joins the centre of a circle to its edge.
- 'radius' ✓
Which of the following formulae calculates the circumference of a circle, when the radius is known?
- $C=$ $1 \over 2$ $\pi r$
- $C = \pi r$
- $C = 2\pi r$ ✓
Which two calculations could be used to find the area of the parallelogram?
- $a \times b$
- $a \times c$ ✓
- $a \times d$
- $b \times c$
- $b \times d$ ✓
The area of the shape is ______ m $^2$ .
- '16' ✓
The first four digits of $\pi$ are ______.
- 3.141 ✓
- 3.142
- 4.143
- 4.145
Select the parallelogram with the smallest area.

Which is a correct formula for calculating the area of a circle?
- $A = \pi d$
- $A = \pi d^2$
- $A = \pi 2r$
- $A = \pi r^2$ ✓
$The area of the circle is equal to the area of the parallelogram. The circumference of the circle is 12<Math>\pi</Math> cm. The base of the parallelogram is <span class="blank">______</span>.$

The area of the circle is equal to the area of the parallelogram. The circumference of the circle is 12 $\pi$ cm. The base of the parallelogram is ______.
- 6 $\pi$ cm ✓
- 12 $\pi$ cm
- 24 $\pi$ cm
The area of the square is 10 cm. The area of the circle is ______.
- 10 $\pi$ cm $^2$ ✓
- 20 $\pi$ cm $^2$
- 100 $\pi$ cm $^2$
- 400 $\pi$ cm $^2$
A circle has radius 6 cm. What is the area of the circle?
- 6 $\pi$ cm $^2$
- 12 $\pi$ cm $^2$
- 36 $\pi$ cm $^2$ ✓
- 144 $\pi$ cm $^2$
Which circle has an area of 9 $\pi$ cm $^2$ ?
$The area of the circle is <span class="blank">______</span><Math>\pi</Math> cm<Math>^2</Math>.$

The area of the circle is ______ $\pi$ cm $^2$ .
- '81' ✓

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A circle can be cut into congruent sectors that are placed together to make a parallelogram.
The length of the parallelogram is half the circumference of the circle.
The height of the parallelogram is the radius of the circle.
The formula for the area of a circle can be derived from the area of this parallelogram.

Pupils may confuse the formula for area with the 2πr version of the formula for circumference.

Area is a 2-dimensional space so its formula requires the multiplication of two lengths. This happens when we square the radius.

Area - Area is the size of the surface and states the number of unit squares needed to completely cover that surface.
Radius - The radius of a circle is any line segment that joins the centre of a circle to its edge.
Diameter - The diameter of a circle is any line segment that starts and ends on the edge of the circle and passes through the centre.