1. Target: Use proportions to calculate the area of sectors.

2. Warm-Up Find the area: How many degrees are in a circle?

3. Sector: Think “a slice of pizza”

4. 5 cm

5. The area of the circle is 60 cm 2. Use a proportion to find the area of the sector.  Write a proportion.  Set the cross products equal.  Multiply.  Divide.  The area of the sector is 15 cm 2.

6. The Macy family bought a family-sized chocolate chip cookie for dessert. Erin ate a slice of the cookie with a central angle of 37 ⁰. The entire cookie had an area of 249 square centimeters. Find the area of Erin’s slice to the nearest hundredth.  Write a proportion.  Set the cross products equal.  Multiply.  Divide.  The area of Erin’s slice was approximately 25.59 cm 2.

7. Find the area of the shaded sector in  M. Round to the nearest hundredth.  Find the area of the circle. A = πr 2 = (3.14)(4) 2 ≈ 50.24 in 2  Write a proportion.  Set the cross products equal. 5777.6 ≈ 360x  Solve by dividing by 360. 16.05 ≈ x  The area of the sector is 16.05 in 2.

8. Write a proportion and find the area of each sector. 1. Area of the circle is 37.8 cm². 2. Use 3.14 for . 12 km

9.  What is a sector?  Describe how to find the area of a circle when the area of the sector is given and the degree of the sector is known.

10. 1. The scale factor between  A and  C is 4 : 3. The circumference of  A is 45.8 m. a. Write a proportion that can be used to find the circumference of  C. b. Find the circumference of  C. 2. The diameters of two circles are 14 ft and 6 ft. The area of the large circle is 153.86 ft². Find the area of the small circle.