A study by the Partnership for a Drug-Free America indicated that, in 1998, 42% of teens in grades 7 though 12 had recently used cigarettes. A similar study in 2005 indicated that 22% of such teens had recently used cigarettes. Write a linear model that relates the percent of teens that recently used cigarettes y to the number of years after 1998, x.

Question

A study by the Partnership for a Drug-Free America indicated that, in 1998, 42% of teens in grades 7 though 12 had recently used cigarettes.  A similar study in 2005 indicated that 22% of such teens had recently used cigarettes.  Write a linear model that relates the percent of teens that recently used cigarettes y to the number of years after 1998, x.

mathteacher1729 · Answer

Consider 1998 as year "zero".  That means 2005 is year "seven". 

The question is now this: 

Find the equation of the line through the points: 

(0,42) and (7,22)

Hope this helps. :)

anonymous · Answer

if we assume x as year and y as percentage we have 2 points (1998,42) & (2005,22) 
so y=(-20/7)*(x-1998)+42.

anonymous · Answer

Thank you very much :)