Circumference Review

Review

• What is the relationship between a radius and a diameter?

• What does a circumference measure?

• What formulas do we use to calculate circumference?

• What do we use to represent pi?

Pi Equals?

• π = circumference/diameter

≈

• π ≈ 22/7 or 3 and 1/7

• We will use 3.14

3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117067982148086513282306647093844609550582231725359408128481117450284102701938521105559644622948954930381964428810975665933446128475648233786783165271201909145648566923460348610454326648213393607260249141273………. (on and on and on)

Find the Circumference of the circle.

rC 2

214.32C

yd. 56.12CBACK

Find the circumference using the diameter.

π dC

1014.3C

in. 4.31C

BACK

Calculate the following

• Using 3.14 for pi.– r = 6– r = 13

• Using 22/7 for pi. – r = 8– d = 24

Circumference 2 Assignment

• Use 3.14 for pi1) r = 4

2) r = 7

3) r = 9

4) d = 15

5) d = 22

6) d = 30

• Use 22/7 for pi1) r = 4

2) r = 7

3) r = 9

4) d = 15

5) d = 22

6) d = 30

Area of a Circle

Area

• The number of square units the figure covers

Area of a Circle

2 rA 2514.3A

2514.3A2in. 5.78A

Find the Area of the circle.

2 rA 2214.3A

414.3A2yd 56.12A

Find the Area of the circle.

2 rA

2814.3A

6414.3A2ft. 96.200A

Practice Problems

• Using 3.14 for pi– r = 6– d = 14

• Using 22/7 for pi– r = 8– d = 24

Area of a Circle1 Assignment

• Use 3.14 for pi1) r = 4

2) r = 9

3) d = 16

4) d = 22

• Use 22/7 for pi1) r = 4

2) r = 9

3) d = 16

4) d = 22

Area of a Circle