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INSTRUCTORS Carleen Eaton Grant Fraser Eric Smith
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For more information, please see full course syllabus of Algebra 1
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Post by Dania Aljilani on December 11, 2013


Ratios and Proportions

  • A ratio is a comparison of two quantities by division.

  • A proportion is an equation stating that two ratios are equal.

  • Two ratios are equal if and only if their cross products are equal. To solve a proportion, use the fact that the cross products are equal. Set the cross products equal to each other and solve for the unknown value.

  • A rate is a ratio of two quantities having different units of measurement.

  • Solve problems involving rates by using proportions.

  • A scale is a ratio that compares the size of a model to the size of the actual object. Proportions can be used to solve problems involving scales.

Ratios and Proportions

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Definitions 0:16
    • Ratio
    • Proportion
    • Example
  • Cross Products 3:00
    • Example: Original Proportion
    • Example 2
  • Rates 6:55
    • Example: Gas
    • Example 2: Apples
    • Example 3: Speed
    • Example 4: Cookies
  • Lecture Example 1 9:17
  • Lecture Example 2 11:53
  • Additional Example 3
  • Additional Example 4