In 1960, there were 450,000 cases of measles reported in the U.S. In 1996, there were 500 cases reported. How many cases of measles would have been reported in 1987 if the number of cases reported from 1960 to 1996 decreased linearly?
Linearly means we can just get the average per year and then multiply by the number of years...
from 1960 to 1996 is 36 years
450 000 to 500 is a drop of 449500 cases
-449 500 / 36 = - 12486.11 cases per year
from 1960 to 1987 is 27 years
450 000 - 27 yr * 12486.11 cases/year = 112875 cases