Area of Circle

Take your notebook and folder from your cubby. Then:

JOKE of the DAYWhat do you get when you cross an insect with

the Easter bunny?Do Now

Find the RADIUS, DIAMETER, CIRCUMFERENCE, and AREA of the circle to the right

5cm

Take your notebook and folder from your cubby. Then:

JOKE of the DAYWhat do you get if you divide

the circumference of a jack-o-lantern by its diameter?Do Now

Find the RADIUS, DIAMETER, and CIRCUMFERENCE of the circle to the right

14ft

Agenda

• Do Now/ Hook: 5 min• Notes: 10 – 15 min• Explore: 15 min• Guided Practice: 15 min• Clean Up: 5 min

We are a TEAM of CONFIDENT PROBLEM SOLVERS & EFFECTIVE COMMUNICATORS2 minutes

Announcements

• HW Due Monday• Quiz

Tuesday/Wednesday• Tutoring Sign Ups• Tickets & Auction

FRIDAY

We are a TEAM of CONFIDENT PROBLEM SOLVERS & EFFECTIVE COMMUNICATORS2 minutes

Parts of a Circle – Review

Radius: Distance from the center to the edge of the circler = d/2

Diameter: Distance across the center of the circled = 2r

Circumference: Perimeter of circle, distance aroundFormula: C = 2 * r * π

Pi (π): Ratio of circumference to diameter. Always equals 3.14

Area: Space inside a figure. Formula for

circles: A = π * r2

Today’s Formula: Area = Pi * Radius Squared

A = π * r2

Examples

Area Explore

1. Trace the circular item on your graph paper2. With a ruler, measure the radius of the circle (from

the center of the circle to the edge). Record your answer in inches in your notebook

3. Using the A = π * r2 formula, calculate the expected area of the circle. Record your answer in inches in your notebook

4. Look at how many square boxes make up the area of this circle. Estimate how many complete square boxes are inside the circle.

5. Compare the expected Area from the formula with the actual measured Area from Step 3

Whiteboard Practice• Show work• Use markers only for the math• Do not raise boards until I count to 3• Cap markers and flip boards over when we go

over problems

Question 1

What is the area of this circle?

A. 6 inches squaredB. 28.2 inches squaredC. 18.8 inches squaredD. 9.4 inches squared

A = π * r2

3in

Question 2

What is the area of this circle?

A. 144 π inches squaredB. 36 π inches squaredC. 6 π inches squaredD. 3 π inches squared

A = π * r2

6in

Question 3

What is the area of this circle?

A. 2463 feet squaredB. 22 feet squaredC. 44 feet squaredD. 153.9 feet squared

A = π * r2

14ft

Question 4

Khyren made a pizza with a diameter of 10 inches. What is the area of his pizza?

A. 78.5 inches squaredB. 314 inches squaredC. 17.2 inches squaredD. 25 inches squared

A = π * r2

Question 5

Mycynthia is building a circular bird pool in her backyard. If the distance from the center of the pool to the edge is 4ft, what is the area of the pool?

A. 25.1 feet squaredB. 50.3 feet squaredC. 16 feet squaredD. 12.6 feet squared A = π * r2

Independent Practice

• Work independently or with your table• Stay seated and raise your hand silently if you

have a question• When finished, work on challenge problems

(on back)