CIRCLES 7 G 4 VOCABULARY Diameter distance across

CIRCLES 7 -G 4

VOCABULARY Diameter -distance across a circle through the center Radius -distance from the center of the circle to the edge Circle Circumference -distance around the outside of a circle Area -space inside a circle

EX. 1 FIND THE DIAMETER (MULTIPLY THE RADIUS BY 2)

EX. 2 FIND THE RADIUS. (TAKE HALF OF THE DIAMETER. ) 24 22 cm 15 m

PI Circles have a special variable that we use to calculate circumference and area. It is called pi or π The value of π is 3. 14

CIRCUMFERENCE EX. 3 Circumference is the distance around the outside of a circle. Formula: C = πd or C = 2πr 5 cm C = πd = (3. 14) (5) = 15. 7 cm

EX. 4 FIND THE CIRCUMFERENCE r = 8 cm C = 2πr = (2) (3. 14) (8) = 50. 24 cm

EX. 5, 6, AND 7 FIND THE CIRCUMFERENCE. 16 in 7 ft 2. 4 mm

EXIT SLIP – FIND THE CIRCUMFERENCE. SHOW YOUR WORK 1. ) d = 12 cm 2. ) r = 10 ft 3. ) r = 4. 5 m

AREA OF A CIRCLE 7 -4 G

SQUARING A NUMBER 32 does NOT mean 3 • 2!!! 32 means 3 • 3 which is 9. a. ) 72 b. ) 52 c. ) 102

AREA FORMULA EX. 1 Area is the amount of space inside the circle. Formula: A = π r 2 or π • r 4 in A = (3. 14)(42) = (3. 14) (16) = 50. 42 in 2

EX. 2 AND 3 FIND THE AREA. 9 m 12 cm

EX. 4, 5, 6 FIND THE AREA. 4. 8 cm 5 mm 14 yd

EXIT SLIP – FIND THE AREA. SHOW YOUR WORK. 1. ) r = 2 mm 2. ) r = 2. 9 in 3. ) d = 26 ft