Ask students to identify variables as they watch Futures Channel Movie #2007 Bats. (You may need to review the concept of variable as a quantity which is not always the same.). In subsequent discussion, elicit or present the variables of “total population”, “number of bats that die each year”, “number of bats born each year”, and time (in years).
Pose this question: Suppose the population of bats in a certain area in the year 2000 was 5000. If d bats die every year, and b bats are born every year, how would you represent the population 5 years later? Guide students to agreement that the new population would be given by this expression (review the concept of expression as a collection of numbers, variables and operations that stands for a quantity):
5000 – 5d + 5b
Tell students that the purpose of the subject of algebra is to make it possible to exactly describe relationships among variables, so that people can do things like predict the future population of an endangered species. Tell them that in this first chapter they will be learning more about how to work with expressions and equations. |
