# Circles for SQA National 5 Maths 1. Radius and diameter of a circle
2. Circumference of a circle
3. Area of a circle

The radius of a circle is the distance between the centre of a circle and the edge. The diameter of a circle is the distance between two edges of a circle passing through the centre. The diameter is double the size of the radius. The circumference of a circle can be calculated using the following formula: C = 2πr, where r is the radius of a circle. The area of a circle is given by the formula: A = πr², where r is the radius of the circle. # 1

Calculate the area of a circle with radius 5 cm.

A = π(5 cm)² = 25π cm² = 78.5 cm² (to 3 significant figures). # 2

Given that r = 8 cm, calculate the circumference of the given circle.

C = 2π(8 cm) = 16π cm = 50.3 cm (to 3 significant figures). # 3

Sketch a diagram of a circle, labelling for its radius and diameter.

image # 4

Given that the radius of a circle is 4 cm, calculate the length of its diameter.

Diameter = 2(4) = 8 cm. # 5

Use the given diagram to calculate the diameter of the circle.

The radius of the circle is 1.2 m.
So, the diameter = 2(1.2) = 2.4 m. End of page