Lesson 10.1, For use with pages 521-526

Find the area of the triangle and rectangle.

1.

4 ft

3 ft 2.

15 m

15 m

Lesson 10.1, For use with pages 521-526

Find the area of the triangle and rectangle.

ANSWER 6 ft2

ANSWER 225 m2

1.

4 ft

3 ft 2.

15 m

15 m

Bell Work

Talk with your partner about the homework that is due today. If it is a book assignment, please open your book

so you can look back at the question.

Discuss each of the following questions with each problem from homework:

How did you solve the problem?

Why did you solve it that way?

What did you get for your answer?

Circles10.2

How would you define a circle?

How do you know where the center of a circle is located?

The distance across the center of a circle is called the diameter. (Line segment AB below)The distance from the center to the edge of a circle is called the radius. (Segment CD)

TWO RADII = One Diameter

or the radius is ½ diameterD ÷ 2 = R

D

A

C

B

The distance around a circle is called the circumference.

C = d or C = 2 r

C = d or C = 2 r

Find the circumference: (round to nearest tenth)

r = 4 in C = 2 r

C = 3.14 x 2 x 4

C= 25.1 in

C = d or C = 2 r

Find the circumference:(round to nearest tenth)

d = 7 cm C = d

C = 3.14 x 7

C= 22.0 cm

Area of a circle is still the number of SQUARE UNITS inside the closed figure.

The area formula is A = r2

read Pi times the radius squared and it means Pi x radius x radius

A = r2

Find the area of the circle below

D = 10 in

A = r2

A = 3.14 x 52

A=78.5 in sq

A = r2

Find the area of the circle below

r = 3 cmA = r2

A = 3.14 x 32

A= 28.3 in sq

GUIDED PRACTICE for Examples 1 and 2

Find the area and circumference of the circle. Use 3.14 for л.

SOLUTION

A = лr 2

1. r = 7 ft

= 3.14 (7)2

= 153.9 ft2.

C = 2лr

= 2x 3.14 x 7

= 44.0 ft

GUIDED PRACTICE for Examples 1 and 2

Find the area and circumference of the circle. Use 3.14 for л.

SOLUTION

A = лr 2

2. d = 44 m

= 3.14 (22)2

= 1519.8 m2.

C = лd

= 3.14 x 44

= 138.2 m

Homework

Page 529 #4-7 Find both circumference and area for each

problem. ROUND TO THE NEAREST TENTH SHOW YOUR WORK!