7.1 Ratios and Proportions 2011
January 05, 2011
Warm­up:
Multiply.
1. x(x + 5)
2. (x ­ 3)(x + 4) 3. (x ­ 2)(3x ­ 7)
Dec 17­8:31 AM
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7.1 Ratios and Proportions 2011
January 05, 2011
7.1 ­ Ratios and Proportions
Objective: Write ratios and solve proportions.
Jan 31­2:20 PM
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7.1 Ratios and Proportions 2011
January 05, 2011
What is a ratio?
Jan 31­3:29 PM
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7.1 Ratios and Proportions 2011
January 05, 2011
Real World Ratios
see attach
ment
• Aspect ratio (width to height) of your TV/Computer screen
Widescreen TV's have an aspect ratio of 16:9
• Strength­to­weight ratio for materials • Thrust­to­weight ratio for an airplane
• Body Mass Index is a ratio of your
height to your weight squared
Jan 31­3:31 PM
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7.1 Ratios and Proportions 2011
January 05, 2011
Example
• An F­15 aircraft produces 50,000 lb of thrust and weighs 44,500 lbs. What is its thrust­to­weight ratio? Write the ratio two different ways.
Jan 31­4:10 PM
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7.1 Ratios and Proportions 2011
January 05, 2011
Proportions
A proportion is a statement that two ratios are equal.
a c
It can be written as =
b d
Write the proportionality statement for the TV dimensions (Width­to­height):
Widescreen TV dimensions Screen width Screen height 46 " TV 40" 22.5" 55" TV 48" 27" Jan 31­4:49 PM
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7.1 Ratios and Proportions 2011
January 05, 2011
Solving Proportions
1.
2.
3.
4.
5.
x 9
=
4 5
9 3
=
5 x
6.
Jan 31­6:10 PM
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7.1 Ratios and Proportions 2011
January 05, 2011
Jan 5­2:53 PM
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7.1 Ratios and Proportions 2011
January 05, 2011
Applying Proportions
A recipe calls for 4 cups of flour and 6 eggs, but you only have 4 eggs. How much flour should you use?
Jan 31­7:48 PM
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7.1 Ratios and Proportions 2011
January 05, 2011
Scale Factor
A scale factor allows you to find the actual measurement from a scaled object or drawing.
Jan 31­7:48 PM
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7.1 Ratios and Proportions 2011
January 05, 2011
Applying Scale Factors
The architecture drawing at the right shows a scale factor of 1 in. = 16 ft. The length of the bedroom in the drawing is 1.25 inches. What is the length of the actual bedroom? Jan 31­9:49 PM
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7.1 Ratios and Proportions 2011
January 05, 2011
Homework
Pg. 369
#13 ­ 21 odd, 26, 27, 28
& 35 ­ 43 odd
Jan 31­10:10 PM
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Attachments
f­22.mp4