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6 th Grade SPI: 0606.4.4 Calculate with circumferences and areas of circles.

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Presentation on theme: "6 th Grade SPI: 0606.4.4 Calculate with circumferences and areas of circles."— Presentation transcript:

1 6 th Grade SPI: Calculate with circumferences and areas of circles.

2 The circumference of a circle is The distance around a circle Hint: Circumference remember circle around

3 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!

4 The diameter is the distance across a circle through the center.

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

6 HINT: Pi =3.14

7 Two formulas are used in finding the circumference of a circle. Circumference = d 3.14 x 4in. 12.6in. WHEN THE CIRCLE HAS A DIAMETER MEASUREMENT, USE THE FOLLOWING FORMULA. 4in.

8 Circumference = 2 r When the radius of a circle is given, the following formula should be used. 2 x 3.14 x 5cm 31.4cm HINT: Always round your answers to the nearest tenth.

9 NOW…Lets have some fun. Tell me what formula would be used to solve the next five problems.

10 3in C = 2 x 3.14 x r

11 8ft C = 3.14 d

12 122mm C = 2 x 3.14 x d

13 17.5 cm C = 3.14 x d

14 122.5mm C = 2 x 3.14 x r

15 Now that we have determined the correct formula for each, lets work the problems.

16 3in C = 2 x 3.14 x r The answer is: 18.8in

17 8ft C = 3.14 d The answer is: 25.1ft

18 122mm C = 2 x 3.14 x d The answer is: 766.2mm

19 17.5 cm C = 3.14 x d The answer is: 55cm

20 122.5mm C = 2 x 3.14 x r The answer is: 76,930mm

21


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