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Ratios & Rates of Change

Chapter 11, Section 2, 3, 4

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Ratio

A ratio is a comparison of like or unlike quantities.

It can compare a part to a part, a part to a whole, or the whole to a part.

Does this sound like something else we have studied about?

• A FRACTION• This can be written as a fraction (3/9) or 3 to 9 or

3:9.

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Practice

• Let’s write a ratio of the number of people with blond hair to the number of people with black hair.

• Boys to girls

• Basketball players to non basketball players

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Equal Ratios

• We can find equal ratios that show the same comparison.

• For the ratio 18:24

18

24

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Rates

• A rate is a ratio that compares unlike units.• A common rate is miles per hour.• If the comparison is to one unit, it is called

a unit rate.• Example: Give the unit rate for 22 laps in 5

minutes.22 laps = laps5 minutes 1 minute

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Practice

• Write each rate as a unit rate.

15 books in 3 weeks

8 visits in 5 days

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Constant or Vary

• What does constant mean?

• What does vary mean?

• Constant-to stay the same

• Vary-to change