Unit 3

  • Ratios, Rates, Unit Rates, Proportions, Percents

    Ratios

    A ratio is a comparison of two things. We might compare boys to girls, cars to trucks or hours asleep to hours awake.
    Whatever we choose to compare can then be written as a ratio. There are three different forms.  A ratio can be written as a to b, a : b or  

    Ratios can be part-to-part, part-to-whole, or whole-to-part.   For more on ratios, visit https://www.mathsisfun.com/numbers/ratio.html

    Quick game to help students recognize ratios:  http://www.mathplayground.com/ASB_RatioMartian.html

  • Proportions

    proportion is an equation stating that two ratios are equivalent.    

    4 dogs:1 cat = 12 dogs: 3 cats is a proportion.

    We usually write proportions in fraction form because it is easier to work with them that way.    

    We can use Cross Multiplication to solve a missing part of a proportion:

    Multiply across the known corners,  then divide by the third number.  And we get this:  (42 × 10) / 20 = 420 / 20 = 21

    Mathisfun https://www.mathsisfun.com/algebra/proportions.html

    Proportions Dirt Bike Racing Game: http://www.mathplayground.com/ASB_DirtBikeProportions.html

    Proportions practice in IXL: https://www.ixl.com/math/grade-7/solve-proportions-word-problems