Chapter 3 Lesson 7Using Formulaspgs. 131-136

Chapter 3 Lesson 7Using Formulaspgs. 131-136

What you will learn:

Solve problems by using formulas

Solve problems involving the perimeters & areas of rectangles

What you will learn:

Solve problems by using formulas

Solve problems involving the perimeters & areas of rectangles

Vocabulary:Vocabulary:

Formula (131): an equation that shows a Relationship among certain quantities. A formula

Usually contains two or more variables.

• Perimeter (132): the distance around a geometric figure

• Area (132): the space inside a geometric figure

expressed as square units

Formula (131): an equation that shows a Relationship among certain quantities. A formula

Usually contains two or more variables.

• Perimeter (132): the distance around a geometric figure

• Area (132): the space inside a geometric figure

expressed as square units

Key Concept (131)Distance Formula

Key Concept (131)Distance Formula

Words: Distance equals the rate multiplied by the time

Variables: Let d= distance, r = rate, & t = timeEquation: d = rt

Words: Distance equals the rate multiplied by the time

Variables: Let d= distance, r = rate, & t = timeEquation: d = rt

What is the rate in miles per hour of a dolphin that travels120 miles in 4 hours?

d = rt120 = r4 Make it look pretty! 4r = 120

4r = 1204 4 r = 30

The dolphin travels at a rate of 30 mph

Key Concept (132):Key Concept (132):

Perimeter of a Rectangle

Words: The perimeter of a rectangle is twice the sum of the length and width

Symbols: P = l + l + w + w Use the way

you or P = 2l + 2w prefer!

or P = 2 (l + w) l

Model: w

Perimeter of a Rectangle

Words: The perimeter of a rectangle is twice the sum of the length and width

Symbols: P = l + l + w + w Use the way

you or P = 2l + 2w prefer!

or P = 2 (l + w) l

Model: w

Key Concept (132):Key Concept (132):

Area of a Rectangle

Words: The area of a rectangle is the product of

the length and width

Symbols: A = lwl Remember area is

Model: w expressed in square units

Area of a Rectangle

Words: The area of a rectangle is the product of

the length and width

Symbols: A = lwl Remember area is

Model: w expressed in square units

Apply what you know! Find the perimeter of arectangle.

8 ft.

4 ft

The perimeter of this rectangle is 28 meters. Its width is 8 meters. Find the length.

P = 2(l + w)P = 2(8+4)P = 2(12)P = 24 ft.

P = 2(l+w)28 = 2(l+8)

28 = 2l + 16

28 - 16 = 2l +16 - 16

12 = 2l 2 2 6 = l

8m

Check:24 = 2(8+4)24 = 2(12)24 = 24

28 = 2(6+8)28 = 2(14)28 = 28

Apply more of what you know!

Find the area of the rectangle:

12 in.

10 in.

A = lwA = 12(10)A = 120 in2

The area of a rectangle is 323 square yards. Its length is 17 yards. Find the width.

A = lw323 = 17w323 = 17w w = 19 yds 17 17

Check:

A = lw323 = 17(19)323 = 323

Check:120= 12(10)120 = 120

Find the perimeter and area of each rectangle:

6 mi

4 mi

18 in.

50 in.

A= lwA = 6(4)A = 24 mi2

P = 2(l+w)P = 2(6 + 4)P = 2(10)P = 20 mi

Check:20= 2(6+4)20= 2(10)20 = 20

P = 2(l+w)P = 2(18 + 50)P = 2(68)P = 136 in.

Check:136 = 2(18+50)136 = 2(68)136 = 136

A= lwA = 18(50)A = 900 in2

Find the missing dimension:

7m

w

P = 24m

A = 176 yd2

w

16yd

P = 2(l+w)24 = 2(7+w)

24 = 14 + 2w24-14 = 14-14+2w10 = 2w 2 2 w= 5m

Check:24=2(7+5)24=2(12)24=24

A = lw176 = 16w176 = 16w 16 16 w = 11yd

Check:176=16(11)176=176

Homework

Quiz Monday!!Test Wednesday!!

Practice Page is by the door!