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3.3 Comparing CD Prices
Name:
Date:
Period:
The ads below use rates to describe sale prices. To compare prices in sales such as these, it’s often useful to
find a unit rate. A unit rate is a rate in which one of the numbers being compared is 1 unit. The comparisons
“45 miles per gallon,” “$3.50 per hour,” “8.5 kilometers per hour,” and “two sandwiches for each person”
are all unit rates. “Per gallon” means “for one gallon” and “per hour” means “for one hour.”
A. Use unit rates to find the cost for one CDs at each store. Which store has the lower price per CD?
B. Fill in the table for each store.
# of CDs
Music City
What happens?
Total Cost
# of CDs
0
0
1
1
2
2
3
3
4
4
5
5
10
10
n
n
CD World
What happens?
Total Cost
C. For each store, write an equation (a rule) that you can use to calculate the cost c for any purchase of n
(any number of) compact discs.
Music City (MC)  ____________________________________________________
CD World (CDW)  ___________________________________________________
D. Suppose a Web site sells CDs for $8.99 per disc. There is a shipping charge of $5 for any order. Fill in the
table.
# of CDs
Web site
What happens?
Total Cost
1
2
3
4
5
10
20
n
E. Write an equation (a rule) that you can use to calculate the cost
compact discs from the web site.
c for any purchase of n (any number of)
F. Write an equation for each store that includes 5% sales tax.
MC  ________________________________________________________________
CDW  _______________________________________________________________
Website  ______________________________________________________________