7.1 Ratios and Proportions
February 05, 2010
7.1 ­ Ratios and Proportions
Objective: Write ratios and solve proportions.
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7.1 Ratios and Proportions
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What is a ratio?
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7.1 Ratios and Proportions
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Real World Ratios
• 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
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7.1 Ratios and Proportions
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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.
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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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Properties of Proportions
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7.1 Ratios and Proportions
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Solving Proportions
1.
2.
3.
4.
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7.1 Ratios and Proportions
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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?
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Scale Factor
A scale factor allows you to find the actual measurement from a scaled object or drawing.
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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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Homework
Pg. 369
#13 ­ 21 odd, 26, 27, 28
& 35 ­ 43 odd
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Attachments
f­22.mp4