# Review Multiplying decimals: 3.2 x 5.12 Multiplying fractions and whole numbers: 5 x 2/3.

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Review Multiplying decimals: 3.2 x 5.12 Multiplying fractions and whole numbers: 5 x 2/3

Circles, Pi, & Circumference

The outside of the circle is called circumference The circumference is the distance around the circle.

The midpoint of a circle is center

The line drawn from the centre to the circumference is … radius

The line drawn from one circumference through the centre to another circumference is … radius diameter The diameter cuts the circle in half!

A line that connects one point on the edge of the circle with another point on the circle is called …. chord The chord that passes through the centre of the circle is the diameter.

A segment ie. part of the circumference of the circle is called an... a r c

Parts of the Circle centre radius diameter chord arc

The Definition of Pi Pi, not Pie. 1.The 16 th letter of the Greek alphabet is P or p, corresponding to the roman p. 2. A number, represented by said letter, expressing the ratio of the circumference of a perfect circle to its diameter. The value of pi has been calculated to many millions of decimal places, to no readily apparent pattern.

Pi Equals? π = circumference/diameter ≈ π ≈ 22/7 or 3 and 1/7 We will use 3.14 3.141592653589793238462643383279502884197169399 3751058209749445923078164062862089986280348253 4211706798214808651328230664709384460955058223 1725359408128481117450284102701938521105559644 6229489549303819644288109756659334461284756482 3378678316527120190914564856692346034861045432 6648213393607260249141273………. (on and on and on)

Use Pi to Find: The area of a circle = πr 2 Circumference of a Circle = πd or 2πr Surface Area of a Sphere, Volume of a Cone, Cylinder and Sphere all are formulas that involve π.

BACK

Find the Circumference of the circle. BACK

Find the circumference using the diameter. BACK

Find the circumference of the circle. BACK

How would you find the diameter of a circle if you were only given the circumference? Find the diameter of a circle that has a circumference of 66. BACK

Find the diameter of the circle below: How to find the diameter given the circumference If you have the circumference: divide the circumference by 3.14 (  ). State the formula Substitute the values for  and C.

Find the circumference of the circle below: How to find the radius given the circumference If you have the circumference: divide this by, , 3.14 first to get the diameter. State the formula Substitute the values for  and C. Then divide the diameter by 2.

Calculate the missing numbers in the table below using the circumference formula below. What’s the formula? 17.584 14.13 5 C (cm)d (cm)r (cm) Use 3.14 as an approximation for . 10 4.5 5.6 2.8 2.25 31.4

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