Rock music accounted for 30.5% of the total sales of recorded music in 1999 , and 20.4% of the total sales of recorded music in 2009 . Find the average rate of change of the percentage of sales of rock music from 1999 to 2009 .
Round to the nearest hundredth of a percent. Note that the percentage sign is already given in the answer, so you do not need to enter it.
The average rate of change is
Round to the nearest hundredth of a percent. Note that the percentage sign is already given in the answer, so you do not need to enter it.
The average rate of change is
