Area of a Circle

Presentation

•

Mathematics

•

7th Grade

•

Medium

•

CCSS

7.G.B.4, HSG.GMD.A.1

Standards-aligned

Courtney Tout

Used 23+ times

FREE Resource

5 Slides • 13 Questions

Area of a Circle

By Courtney Tout

Warm-Up

Open Ended

What do you think about when you hear the word: Area?

Type response here

We can use the circumference formula when given radius:

C = 2 x pi x r

To help us discover the formula for Area of a Circle

Deriving Area of a Circle Formula

Watch as the circle is transformed into a parallelogram and the area of a circle formula is derived.

Multiple Choice

We are taking our circle and its' slices and transforming it to form into a parallelogram. One slice is how tall?

The size of the circumference

The size of pi

The size of the diameter

The size of the radius

Multiple Choice

We are taking our circle and its' slices and transforming it to form into a parallelogram. How long should it be?

The size of the circumference

Half the size of the circumference

The size of the radius

Using the Area of a Parallelogram formula, lets' determine the area of the parallelogram.

We have transformed our circle, into a parallelogram and relabeled.

base = 1/2 C --> 1/2(2Πr)

height = r

1/2 (2)(Πr) (r) = Π x r x r or Πr²

Area of Parallelogram = b x h

Area of Circle = Π x r x r

Area of Circle = Π x r²

Multiple Choice

What is the formula for area of a circle given the radius?

A = πr

A = 2πr

A = πd

A = πr²

Multiple Select

What all information do you need to know to determine Area of a Circle? [Hint: Select 2 choices]

Diameter

Circumference

Radius

Just like with Circumference we set up to solve for Area of a Circle, by plugging things in!

Set-It-Up

We are given a radius of 7 inch
Plug into our Formula
- A = Π x 7² which is the same as A = 3.14 x 7 x 7
Just Multiply to Solve
- Remember ONLY 2 Numbers at a time - what your decimal place!

Multiple Select

Set Up to Find the Area [SELECT ALL THAT APPLY]

$A=\ 3^2\pi\ \ \ \ or\ \ \ \ A\ =\ 9\pi$

$A=2\times\pi\times3\times3$

$A=\pi\times3\times3$

$A=3.14\times3\times3$

Multiple Choice

find the area of the circle below.

100 cm

225 cm

9 cm

28.26 cm

Multiple Choice

What is your radius?

12 cm

10 cm

36 cm

6 cm

144 cm

Multiple Select

Set Up to Find the Area [SELECT ALL THAT APPLY]

$A=\pi\times6\times6$

$A=12\times12\times\pi$

$A=12^2\pi\$

$A=144\pi$

$A\ =\ 6^2\pi$

$A=36\pi$

$A=3.14\times6\times6$

Multiple Choice

What is the area of this circle?

163.2

15.3

124.2

113.1

Multiple Choice

A cruise ship has a large, circular window. It has a diameter of 8 meters.

What is the Radius?

8 m

16 m

64 m

4 m

Multiple Select

A cruise ship has a large, circular window. It has a diameter of 8 meters.

Set It Up:

$A=4^2\pi$

$A=4^2\times3.14$

$A=8\pi$

$A=64\times3.14$

$A=8\times8\times3.14$

Multiple Choice

A cruise ship has a large, circular window. It has a diameter of 8 meters. What is the window's area?

31.25 m²

29.55 m²

30.36 m²

50.27 m²

Area of a Circle

By Courtney Tout

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