Circles

Question 1

What is the line running from the edge of the circle to the middle called?

Answer 1

The radius

Question 2

What is the diameter?

Answer 2

A line from one edge of the circle to the other passing through the middle of the circle

Question 3

What is the measurement around the outside of the circle known as?

Answer 3

The circumference

Try to think of it as the perimeter of the circle

Question 4

The radius is what of the diameter?

Answer 4

Half

Question 5

What is the value of Pi (π) to 2 decimal places?

Answer 5

3.14

Question 6

What happens when we divide the circumference by the diameter (C ÷ D) ?

Answer 6

We should get Pi (π) everytime

Question 7

What is the formula for the circumference of a circle?

Answer 7

Pi (π) x Diameter

Question 8

Tweedledum, Tweedledee, Circumference =

Answer 8

Pi (π) x D

Question 9

What happens when we divide the circumference by the diameter (C ÷ D) ?

Answer 9

We should get Pi (π) everytime

Question 10

What is the formula for the circumference of a circle?

Answer 10

Pi (π) x Diameter

Question 11

Tweedledum, Tweedledee, Circumference =

Answer 11

Pi (π) x D

Question 12

What is the area of a shape?

Answer 12

Everything inside of the shape

Question 13

What is the formula for the area of a circle?

Answer 13

π x r²

Question 14

If the diameter of a circle is 5cm, what is the radius?

Answer 14

2.5cm

Question 15

If the radius of a circle is 10.5m, what is the diameter?

Answer 15

21m

Question 16

If the diameter of a circle is 7m, what is the circumference?

Answer 16

Pi (π) x D

3.14 x 7m

= 21.98m

Question 17

If the radius of a circle is 11 yards, what is the circumference?

Answer 17

We are only given radius so we first need to multiply by 2 to work out the diameter ie 11 x 2 = 22

Pi (π) x D

3.14 x 22 yards

=69.08 yards

Question 18

If the circumference of a circle is 15cm, what is the diameter?

Answer 18

We are working backwards here, so we need to divide by Pi (π) instead of multiplying by Pi (π)

15cm ÷ 3.14

=4.78cm

Question 19

What is the formula for the area of a circle?

Answer 19

π x r²

Question 20

If the circumference of a circle is 15cm, what is the diameter?

Answer 20

We are working backwards here, so we need to divide by Pi (π) instead of multiplying by Pi (π)

15cm ÷ 3.14

=4.78cm

Question 21

If the radius of a circle is 4mm, what is the area of the circle?

Answer 21

π x r²

3. 14 x 4²
4. 14 x 16

=50.24 mm²

Don’t forget to put in the squared in the units of your answer!!!

Question 22

Mr Cullum buys a pizza with a radius of 20cm. He only manages to eat half of the pizza. Work out the area of the remaining pizza.

Answer 22

Always work out the full area first.

π x r²

3. 14 x 20²
4. 14 x 400

=1,256cm²

However, he only ate one half which means one half is remaining. We therefore need to divide the total area by 2 to find out the area of the remaining half.

1,256cm² ÷ 2 = 628cm²