Question

At the end of 2000, Mary had 47 CDs in her music collection. At the end of 2003, she had 83 CDs. She collected an equal number of CDs each year between 2000 and 2003.
What is the rate of change in the number of CDs in Mary’s collection between 2000 and 2003?

Answer 1

Mary collected 12 cd's each year after 2000/47 2001/12 2002/13 2003/12 = 47+12+12+12=83

Answer 2

She accumulated an average rate of 12 CDs each year.  You find this by subtracting 47 from 83 which gives you 36, dividing it by 3, which gives you 12.