4.1 Ratio and Proportion 121807

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4.1 Ratio and Proportion 12/18/07

• Ratio comparison of two numbers by division.
• Can be written
• a to b
• a b
• where b ? 0.
• If a and b represent quantities measured in
  different units, then the ratio of a to b is a
  rate.
  
• A unit rate is a rate with a denominator of 1.
• Ex.

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Using Unit Rates

• Find the rate (cost per ounce).

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Converting Rates

• A cheetah ran 300 feet in 2.92 seconds. What was
  the cheetahs speed in miles per hour?
  
• You need to convert feet to miles and seconds to
  hours.

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Solving Proportions

• A proportion is an equation that states that two
  ratios are equal.
  
• a c for b ? 0 and d ? 0.
• b d
• You read this proportion as a is to b as c is to
  d.
  
• The extremes of the proportion are a and d.
• The means of the proportion are b and c.
• Another way you can see this proportion written
  is a b c d.
  

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Using the Multiplication Property of Equality

• Solve
• multiply by the LCM of 9 and 6,
  which is 18

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Cross Products

• The products ad and bc are the cross products of
  the proportion
  
• For example,

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Using Cross Products

• Use cross products to solve the proportion

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Using Multi-Step Proportions

• Solve the proportion

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More Practice!!!!

• Textbook p. 185 2 28 even, p. 186 32 36
  even.
  
• Homework Worksheet 4.1