The average rate of change is

Question

Rock music accounted for 35.5\% of the total sales of recorded music in 1998, and 29.6\% of the total sales of recorded music in 2008. Find the average rate of change of the percentage of sales of rock music from 1998 to 2008.
Round to the nearest hundredth of a percent

Answer 1

Rate of change involves a unit change over time change - in this case, a percentage per year is what we are looking for.

 

The difference in percentage is 29.6% - 35.5% = ( - 5.9%)

 

The difference in years is 2008 - 1998 = 10 years

 

Going back to what we are looking for, percentage per year, we do ( - 5.9%) / 10 years = -0.59%/year.