Area and circumference of circles

Question 1

If O is the centre of the circle, what is the radius?

Answer 1

The radius is the length that is measured from any part of the circumference of the circle to the centre

Question 2

If O is the centre of the circle, what is the diameter?

Answer 2

The diameter is any line segment that passes through the centre of the circle and the ends points lie on the circle

Question 3

How is the diameter related to the radius of a circle

Answer 3

The diameter is twice the length of a radius

dia = 2 * radius

Question 4

What is π

(pronounced as pi)

Answer 4

It is a ratio of the circumference of the circle to its radius

Question 5

What is the circumference of a circle

Answer 5

The circumference of a circle is the length around it

Question 6

How we find the area of a circle

Answer 6

If we are given the length of the diameter, we have to divide the diameter bty 2 to find the radius first

Question 7

Whats is the circumference of the circle correct to 3 significant figures?

Answer 7

2 * π * 8 = 50.3 cm

Question 8

Whats is the area of the circle correct to 3 significant figures?

Answer 8

π * 8² = 201 cm²

Question 9

Whats is the circumference of the circle correct to 3 significant figures?

Answer 9

radius = 14/2

= 7 c m

2 * π * 7 = 44.0 cm

Question 10

Whats is the area of the circle correct to 3 significant figures?

Answer 10

radius = 7 cm

π * 7² = 154 cm²

Question 11

Whats is the circumference of the circle correct to 3 significant figures?

Answer 11

2 * π * 12 cm = m = 75.4 cm

Question 12

Whats is the area of the circle correct to 3 significant figures?

Answer 12

π * 12² = 452 cm²

Question 13

Whats is the circumference of the circle correct to 3 significant figures?

Answer 13

π * 21 cm = 66.0 cm

Question 14

Whats is the area of the circle correct to 3 significant figures?

Answer 14

radius = 21/2

= 10.5 cm

π * 10.5² = 346 cm²