Ratios and Proportions

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Ratios and Proportions

• Chapter 2

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Ratio comparison of two numbers

• I got 21 out of 24 questions correct!
• Write this ratio as a fraction, with a colon, or
  as a decimal.
• Fraction
• With a colon
• As a decimal
• How do we find the decimal?

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Proportion two equal ratios

• Check to see if its a proportion by comparing
  the decimals
• Check to see if they are equal by comparing the
  fractions

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Can we use the same numbers and create three
other proportions?

• Dont forget to check your proportions by
  comparing the decimals or the fractions

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Solving Proportions

• Cross multiplication
• Only works when there is an equal sign ()
  between two fractions.
• Verify that you are correct

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Try these

• Use cross multiplication to solve
• Compare the fractions or decimals to check

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Set up a proportion to solve

• If Julie pays 4.00 for ½ pound of ham at the
  deli, how much will 1.25 lbs cost?
• Units must be aligned

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Try this

• If 18 pieces of candy weigh 2.13 oz, how much
  will 30 pieces of candy weigh?
• Check by comparing decimals

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Percents as Ratios

• Percent per 100
• Can we write 65 as a ratio?
• What is 3 as a ratio?
• What is as a percent?

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Solve percent questions!

• The proportion can be used to
• answer the question 18 is what percent of 45?
• Remember
• Jean made a 28 out of 35 on a test. What percent
  did she get correct?
• 36 is what percent of 50?

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Write a proportion and solve.

• What is 8 of 14?
• 178 of what number is 49?
• 37 is 15 of what number?

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Here are the proportions. YOU write the
questions.