Investigations with Movie Rentals

Using Excel

Karyn Carson

You want to join a movie club and there are two in your neighborhood.  However, their rates are different and you canÕt decide which one to join.  Here are the ads for each store:

Movies Are Us

No Membership Fees

\$4.50 per rental

Look At Us Video

\$5 Membership Fee

\$3.50 per rental

Where should you take your business?  LetÕs take this information and create an equation (also called a function) so that we can look at this data graphically.  What would the functions be?

Movies are Us:  y = 4.5x

Look at Us Video:  y = 3.5x + 5

LetÕs enter these functions into the spreadsheet program Excel to look at these situations graphically and see if we can determine which store to sign up with.

 Number of Videos Rented Videos are Us Look at Us Videos 1 \$             4.50 \$                  8.50 2 \$             9.00 \$                12.00 3 \$           13.50 \$                15.50 4 \$           18.00 \$                19.00 5 \$           22.50 \$                22.50 6 \$           27.00 \$                26.00 7 \$           31.50 \$                29.50 8 \$           36.00 \$                33.00 9 \$           40.50 \$                36.50 10 \$           45.00 \$                40.00 11 \$           49.50 \$                43.50 12 \$           54.00 \$                47.00 13 \$           58.50 \$                50.50 14 \$           63.00 \$                54.00 15 \$           67.50 \$                57.50 16 \$           72.00 \$                61.00 17 \$           76.50 \$                64.50 18 \$           81.00 \$                68.00 19 \$           85.50 \$                71.50 20 \$           90.00 \$                75.00

As you can see, once youÕve rented 5 videos, the total cost paid at Look at Us drops below the cost at Videos are Us.

At what point on the graph do you see where it becomes better for us to join Look at Us?