Circle Basics

Circles

Calculating Areas and Circumferences

Formula you need to know

The radius of a circle

The measurement from the middle of the circle to the outside of the circle

Multiple Choice

(Calculater if need) You have a radius of 7mm, what is the area?

• 153.9 cm

• 153.9 $$mm^2$$

  $$mm^2$$

• 7mm

• 10 $$mm2$$

Calculate the circumference

The circumference

• The full measurement of the outside of the circle

Multiple Choice

SO FAR WE KNOW..... The radius is....?

• The perimeter of the of the circle

• The area of the circle

• The measurement right across the circle

• Measurement from the middle of the circle to the outside

Multiple Choice

The Circumference is ... ?

• The middle of the circle

• The perimeter of the circle

• The middle to the edge of the circle

• The amount of corners

So what about the diameter?

The diameter is the full length across the circle... simply the radius multiplied by 2

Multiple Choice

So if the radius is 16cm, what is the diameter?

• 32cm

• 32mm

• 45cm

• 1cm

Multiple Choice

If the diameter of a circle was 54mm, what would the radius be?

• 21mm

• 27M

• 27mm

• 13mm

How do we find the Circumference?

:)

Easy?

Poll

What is the Circumference if the diameter is 12cm?

• 37.69cm

• 42.31cm

What if we were only given the radius?

Poll

A radius of 8 is given, what is the Circumference?

• 17.2cm

• 50.3 cm

QUIZ

Multiple Choice

A circle has a radius of 18cm, what is the area?

• 791cm

• 89m

• 1017cm

• 1017

  $$cm^2$$

Multiple Choice

And what would be the circumference if we had a radius of 18cm?

• $$113.04cm2$$  
  

• 110cm

• 113.04cm

• 76.03cm

Multiple Select

What would be the area of a circle with a radius of 4m?

• 50.42m

• 50.24cm

• 50.24m

• 0

Multiple Choice

What about the circumference if we had a diameter of 4m?

• 12.56m

• 13.4

• 10.3

• 7989044mm