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In 1982 the population density of a country was 64 people per square mile,
and in 2002 it was 82 people per square mile.
Use a linear function to estimate when the population density reached 89 people per square mile
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In 20 years from 1982 to 2002, the average rate of increasing population density was
r = = = 0.9 of a person per square mile per year.
So, assuming that this rate remains constant, we write this linear equation for the future density
D = 82 + r*(t-2002).
To find a year when the density will reach 89 p/sq.mile, we write equation
82 + 0.9*(t-2002) = 89,
and we find
t-2002 = = = 7.777...
It tells us that the density 89 p/sq.mile will be reached somewhen in the year 2009 or 2010
depending on from which time moment in the year 2002 we started out our time counter (chronometer). ANSWER
Solved.