Question

Recycled​ CDs, Incorporated, offers a choice of 5 used CDs for ​$28​, with each additional CD costing ​$5. Write a cost function for purchasing 5 or more CDs. What will the cost of buying 9 CDs​ be? Let x represent the number of CDs over 5.

Answer 1

`28 + 5x`
In terms of x

Answer 2

`28+5\text{x}` and
`\$48`

Explanation:

Given: Recycled​ CDs, Incorporated, offers a choice of 5 used CDs for ​$28​, with each additional CD costing ​$5

To Find: cost function for purchasing 5 or more CDs, the cost of buying 9 CDs, Let x represent the number of CDs over 5.

Solution:

Cost of buying 5 used CDs
`=\$28`

Cost of additional CD
`=\$5`
`\text{per CD}`

now,

number of CDs over
`5`
`=\text{x}`

cost function for purchasing
`5` or more CDs =
`\text{fixed cost of 5 CD}+ 5*\text{no. of additional CD}`

`=28+5\text{x}`

Now,

Cost of buying
`9` CDs

one will buy
`4` additional CDs

`=28+5*4`

`=28+20`

`=\$48`

Hence, cost function for purchasing 5 or more CD is
`28+5\text{x}`, and cost of buying
`9` CD is
`\$48`