• Recall: A ratio is simply a quotient of two quantities. The ratio of a to b can be written as a:b or as the fraction ^a⁄_b.

• A few examples of ratios:
  • Using that there are 1,600 students at Wheaton and 140 full-time faculty here, the ratio of students to (full-time) faculty is 1600/140=11.42

    so we would say the student-faculty ratio is ``11.4 to 1'', which we could write as 11.4 or as 11.4:1.

  • Gas mileage is the ratio of miles driven to gallons of gas consumed.

  • Win:loss ratios

• When one ratio is equal to another, we have a proportion.

  In general, if the ratio of a to b equals the ratio of c to d, we have the proportion

  a/b=c/d, and we say a is to b as c is to d..
• Practice Problem: Below is a picture of one of the Bratz (Sharidan).

  Some of Sharidan's measurements: Height: 9" (flat feet) Legs: 5" (flat feet) Head: 2.25" Width of Eye: .625"

  • The average height for an adult female in the U.S. is 5' 3.8", or 63.8". How tall would the average woman's head need to be, to be in the same proportion to her height as Sharidan's head is to her height?

  • Assuming the average woman's head is actually 8.5" from crown to bottom of chin, how wide would each of her eyes have to be, to be in the same proportion to her head as Sharidan's are to her head?

Solutions