Circles

Question 1

What is the formula for the circumference of a circle?

Answer 1

C=πD
or
C=2πr

Question 2

What is the formula for the area of a circle?

Answer 2

A=πr²

Question 3

What is the value of π to 2 decimal places?

Answer 3

3.14

Question 4

How do you find the arc length?

Answer 4

• Find the circumference of the full circle
• Find the fraction of the circumference by using ‘angle/360’

Question 5

How do you find the perimeter of a part circle?

Answer 5

• Find the circumference of the full circle
• Find the fraction of the circumference by using ‘angle/360’
• Add the arc length and the two radii together

Question 6

How do you find the area of a part circle?

Answer 6

Find the area of the full circle

Find the fraction of the area by using
‘angle/360’

Question 7

How do you find the diameter from a given circumference?

Answer 7

Substitute into the formula
C=πD

and solve
(Divide by π)

Question 8

How do you find the radius from a given area?

Answer 8

Substitute into the formula
A=πr²

and solve
(Divide by π and then √ )

Question 9

What are the steps to find the area of the shaded segment?

Answer 9

Calculate:
Area of full circle
Area of sector (quarter circle)
Area of triangle (1/2 base x Height)
Subtract the Triangle from the Sector