Checking and securing understanding of circles | Maths

Starter quiz

Which of these shapes are polygons?

A ✓

B

C

D

E ✓
Which of these statements correctly explains why this shape is not a polygon?

It has more than three sides.

It is 2D.

Polygons are 3D shapes.

It is made up of more than just straight-line segments. ✓

Three of its line segments intersect at a perpendicular right-angle.
$1 centilitre equals <Math>1 \over 100</Math> litres. Match each letter in the ratio table to its value to convert 4040 cl into litres.$

1 centilitre equals $1 \over 100$ litres. Match each letter in the ratio table to its value to convert 4040 cl into litres.

$a$

⇔

$1 \over 100$ ✓

$b$

⇔

4040 ✓

$c$

⇔

40.4 ✓
0.065 litres = ______ centilitres.

'6.5' ✓
The perimeter of this parallelogram is ______ cm.

'64' ✓
The area of this parallelogram is ______ cm².

'200' ✓

Exit quiz

Each diagram shows a different part of a circle. Match each part of a circle to its name.

Diagram a

⇔

segment ✓

Diagram b

⇔

sector ✓

Diagram c

⇔

chord ✓
The length of the diameter of this circle is ______ inches.

'34' ✓
The circumference of a circle is 150 cm. Which of these statements is correct about the circle?

The radius of the circle is 75 cm.

The diameter of the circle is 300 cm.

The diameter of the circle is 150 $\pi$ cm.

An arc from this circle must be less than or equal to 150 cm in length. ✓

An arc from this circle must be greater than or equal to 150 cm in length.
The diameter of a circle is 60 cm. Which of these statements is correct about the circle?

The radius of the circle is 30 cm. ✓

The radius of the circle is 120 cm.

The circumference of the circle is 30 $\pi$ cm.

The circumference of the circle is 60 $\pi$ cm. ✓

The circumference of the circle is 120 $\pi$ cm.
The radius of a circle is 9 cm. Which of these statements is correct about the circle?

The diameter of the circle is 4.5 cm.

The diameter of the circle is 18 cm. ✓

The area of the circle is 9 $\pi$ cm².

The area of the circle is 81 $\pi$ cm². ✓

The area of the circle is 255 cm² (to the nearest integer).
The area of this circle can be calculated from the equation $A = \pi \times 62^2$ . Match each property of the circle to its value.

radius (in cm)

⇔

62 ✓

diameter (in cm)

⇔

124 ✓

circumference (in cm)

⇔

124 $\pi$ ✓

area (in cm²)

⇔

12 076.28 ✓

Worksheet

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Video

Lesson Details

Key learning points

A chord splits the circle into two uneven pieces.
The smaller piece is the minor segment and the larger is the major segment.
Sectors look familiar as you broke a circle into sectors to draw a pie chart.
The circumference of a circle is found using C = πd or C = 2πr
The area of a circle is found using A = πr²

Common misconception

"Any line segment starting from the centre of a circle is a radius."

It is true that one endpoint of a radius must be at the centre of a circle. However, the other endpoint must be on the circumference of the circle. This second endpoint cannot be inside or outside of the circle.

Keywords

Chord - A chord is any line segment joining two points on the circumference of a circle.
Segment - Two segments are created when dividing a circle into two parts using a chord.
Sector - A sector is the region formed between two radii and their connecting arc.
Arc - An arc is part of a curve. An arc of a circle is part of the circle’s circumference.