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If you read about circumferences and pi, you'll no doubt come across circles. In Math, in any circle the ratio of the distance around the curved perimeter to the distance across the circle through the center is the Greek letter π (pi) and has a value of just over 3.

1.

A line which passes through the center of a circle and joins two points on its circumference is called a .......

centre line

circumference

diameter

radius

2.

A circular lawn has a 20 m radius. What is the approximate circumference of the lawn?

100 m

126 m

150 m

175 m

Using C = 2 π r, 2 x 3.141592 x 20, C = 125.66 m

3.

A round table has a diameter of 200 cm. What is the approximate circumference of the table?

286 cm

628 cm

1,256 cm

I need to know the radius first

Using C = 2 π r, 2 x 3.141592 x 100, C = 628.3184 cm. Remember to use radius and not diameter!

4.

What is the correct formula for the circumference of a circle?

C = 2πr

C = 2πd

C = 2π

C = 3πr

5.

A line which joins the center of a circle to a point on the circumference is called a .......

centre line

diameter

half distance

radius

6.

What is the area of a circle with a radius of 7 cm (to one decimal place)?

53.9 cm

153.9 cm

315.9 cm

513.9 cm

The radius = 7 cm, so the calculation is: 3.141592 x 7 x 7 = 153.938 cm

7.

The distance measured around a circle is called the .......

brim

circumference

diameter

radius

8.

To the nearest square meter, what is the area of a circular pool with a radius of 10 m?

114 m^{2}

214 m^{2}

314 m^{2}

414 m^{2}

The radius = 10 m, so the calculation is: 3.141592 x 10 x 10 = 314.159 m^{2}

9.

What can be calculated using π r^{2}?

Area of a circle

Circumference of a circle

Diameter of a circle

Volume of a circle

Remember to use the radius of the circle and not the diameter

10.

The area of a circular lawn is 628 m^{2}. How far is it across to the nearest meter?

20

24

28

32

Remember, you are asked for the diameter not the radius

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