The percentage of college students who are age 35 and older has been increasing at roughly a linear rate. In 1972 the percentage was 9% and in 1998 it was 17%

Question

Find an equation giving the percentage of college students age 35 and older in terms of t where t represents the number of years since 1972

Answer 1

1998-1972=26 years, and 17%-9%=8%.

So the rate of percentage increase is 8/26=4/13% per year.

A linear function might look like f(t)=9+4t/13 percent for years since 1972.