Answer
According to the formula, the percent of American adults who used smart phones to go online in $2012$ is 55.4%.
Work Step by Step
The calculated value overestimates the actual value by 0.4%.
Consider $S=32+8.7x-0.3{{x}^{2}}$.
Number of years from $2009$ to $2012$ = $3$years.
So, put $x=3$in the given formula.
\[\Rightarrow S=32+8.7(3)-0.3{{(3)}^{2}}\]
$\Rightarrow S=32+8.7\times 3-0.3\times 9$
$\Rightarrow S=32+26.1-2.7$
$\Rightarrow S=55.4\,percent$
The actual percent shown in the bar graph is 55%, which is greater than the calculated value.
Find the difference of both values.
$=55.4percent-55percent\,\,=\,\,0.4percent$
So, the calculated value underestimates the actual value by $0.4\,percent$.
