Warm Up: Perimeter *Perimeter is the distance around a polygon *Find perimeter by adding the length of the sides together* 1.

57 km 38 km 2.

22 cm 67 cm 22 cm 3. 49 cm 49 cm 54 cm 96 cm

4.

78 m

5.

18 cm

6.

14 cm 77 cm Hexagon (all sides the same) Square/Diamo nd Parallelogram

Lesson 4.2: Area I can:



Find the area of a circle, triangle, square, and quadrilaterals using their formulas.

Vocabulary:



Area



Base



Height



Altitude

Area

The amount of space inside an object.

The number of square units it takes to completely fill a space.

Area of a Circle

A

 

r

2 *On Friday, we learned how to find the circumference of a circle, or the part shown in black; today we are learning how to find the area, or the red part.

Find the Area

You are given the radius, find the area.

15

A

 

r

2

A

   15 2

A

 225  

A

 225  3 .

14

A

 706 .

5

Find the Area

You are given the diameter, find the area.

4

A

 

r

2

A

   2 2

A

 4  

A

 4  3 .

14

A

 12 .

56

Find the Area

13 6

Base

The side of a figure that is perpendicular to the height/altitude.

Height

The distance from the top of an object to its base. h b

Altitude

Height of an object.

Area of a Triangle

Think about this:

A

= 1 2 ×

b

×

h

h rectangle?

b How many triangles are in a What is the area of a rectangle?

What would the area of ONE triangle be?

Find the Area

6 A=7 7 2 3 A=9 3 8 A=12

Find the Area

2 4 6 3