Since 2009 the number of smartphones shipped from manufacturers to stores around the world has increased exponentially. The growth

from 2009 through 2015 can be modeled using the function () =

174 • 1.67 where t is the number of years since 2009 and () is

measured in millions of smartphones.

Explain a way you could calculate exactly when smartphone manufacturers were shipping 500

million smartphones to stores around the world.