Story problem

Question

Stacy buys 3 CD 's in a set of $29.98. She saves $6.44 by buying the set instead of buying the individual CD 's. If the CD 's cost the same amount how much does each of the three CD 's cost when purchased individually? We keep coming up with$12.14

Answer 1

Hi Nathian. The answer of $12.14 seems to be correct, assuming the problem is asking how much one CD costs (outside of a set).  Is there a different answer you're suppose to get?

 

This is how you would normally solve this problem: figure out what you know first, create a formula with variables, and plug in the variables.

 

------

 

First, we know that the following is true:

 

We don't know how much 1 CD (x) costs

x = ?

 

The set of 3 CDs (y) costs $29.98

y = $29.98

 

Buying the set (y) is $6.44 cheaper than buying 3 CDs (3x) separately

y + $6.44 = 3x

OR

3x - $6.44 = y

OR

3x - y = $6.44

 

 

When you plug in y = $29.98 into either formula, you'll get...

 

y + $6.44 = 3x

$29.98 + $6.44 = 3x

$36.42 = 3x

$36.42 ÷ 3 = 3x ÷ 3

$12.14 = x

 

OR

 

3x - $6.44 = y

3x - $6.44 = $29.98

3x - $6.44 + $6.44 = $29.98 + $6.44

3x = $36.42

3x ÷ 3 = $36.42 ÷ 3

x = $12.14

 

OR

3x - y = $6.44

3x - $29.98 = $6.44

3x - $29.98 + $29.98 = $6.44 + $29.98

3x = $36.42

3x ÷ 3 = $36.42 ÷ 3

x = $12.14