Chapter 6: Ratios, Proportions, and Percents

#2006, Cheetahs - To help save an endangered species like the cheetah, you must start by understanding its behavior.

Tell students that you are going to show a short video about a woman that has an interesting job and you want them to describe that job to you after its over.  Show Futures Channel Movie #2006, Cheetahs. 

Discuss students’ descriptions of the job, and guide the class to agreement that she is trying to help the cheetah species by helping male and female cheetahs to reproduce.

Explain that, in the wild, cheetahs are in trouble because only about a quarter of young cheetah cubs survive to become adults.  Ask, “Suppose we have two areas in Africa where cheetahs live in the wild.  In one area there are 240 cubs born one year, and 64 of them survive.  In the other area there are 300 subs born, and 72 of them survive.  Which is a safer area for cheetah cubs?”

Explain that you can compare survival rates with fractions (64/240 and 72/300), but it is difficult to tell which is better because the fractions don’t all have the same denominator.

Ask “Wouldn’t it be easier if we converted all of our fractions to the same denominator so we could compare them easily?”.  Then explain that we actually do just this, and the denominator that we use is 100.  Tell students that there is a special word we use in math to talk about fractions with denominators of 100, and that word is “percents”.