Question

The graph below shows the average Valentine’s Day spending between 2003 and 2012

Answer 1

The average rate of change of a graph between two intervals is given by the difference in value of the values on the graph of the two interval divided by the difference between the two intervals.

Part A.

From the graph the average Valentine's day spending in 2005 is 98 while the average Valentine's day spending in 2007 is 120.

The average rate of change in spending between 2005 and 2007 is given by

$\frac{120-98}{2007-2005} = \frac{22}{2} =\ 11/year$



Part B

From the graph the average Valentine's day spending in 2004 is 100 while the average Valentine's day spending in 2010 is 103.

The average rate of change in spending between 2004 and 2010 is given by

$\frac{103-100}{2010-2004} = \frac{3}{6} =\ 0.5/year$



Part C:

From the graph the average Valentine's day spending in 2009 is 102 while the average Valentine's day spending in 2010 is 103.

The average rate of change in spending between 2009 and 2010 is given by

$\frac{103-102}{2010-2009} = \ 1/year$