This lesson continues to examine quantities that decrease exponentially. They use the distributive property to rewrite expressions in which a quantity decreases by a factor of itself. For example, a $500 computer that loses of its value each year could be written as or as . An expression using only multiplication is easier to extend to multiple applications of the growth factor.

Using an exponent to express repeated decrease by the same factor is a good example of a generalization based on repeated calculation (MP8). Writing expresses the computation of repeatedly decreasing by , times.