Area and Circumference of a Circle

Area and Circumference of a Circle - Transcript

6th Grade SPI 0606 4 4 Calculate with circumferences and areas of circles

The circumference of a circle is

The distance around a circle
Hint Circumference remember circle around

First we must define some things about a circle
The radius is the distance from the center of a circle to any point on a circle
Hint I like to define it as halfway through

The diameter is the distance across a circle through the center

We use Pi as the measurement to help us find the circumference of a circle
Pi not Pie

HINT Pi 3 14

WHEN THE CIRCLE HAS A DIAMETER MEASUREMENT USE THE FOLLOWING FORMULA

Two formulas are used in finding the circumference of a circle d
3 14 x 4in 12 6in
4in

Circumference

When the radius of a circle is given the following formula should be used Circumference 2 r
2 x 3 14 x 5cm 31 4cm
HINT Always round your answers to the nearest tenth

NOW Let s have some fun

Tell me what formula would be used to solve the next five problems

3in

C 2 x 3 14 x r

8ft

C 3 14 d

122mm

C 2 x 3 14 x d

17 5 cm

C 3 14 x d

122 5mm

C 2 x 3 14 x r

Now that we have determined the correct formula for each let s work the problems

The answer is 18 8in

3in

C 2 x 3 14 x r

8ft

C 3 14 d The answer is 25 1ft

122mm

C 2 x 3 14 x d The answer is 766 2mm

17 5 cm

C 3 14 x d The answer is 55cm

122 5mm

C 2 x 3 14 x r The answer is 76 930mm