Math Help for Section 3.4, Page 130

Unit
Prices
As a consumer, you must be able to determine the unit prices of items
you buy in order to make the best use of your money. For two
different amounts of the same product, the one with a lower unit price
is the
“best buy.”

Example
3: Tip

You could calculate unit price per pound instead of per ounce.

    $\displaystyle{\text{Unit price}} = {{{\text{Total
price}}} \over {{\text{Total units}}}} = {{\$ 7.14} \over
{5{\textstyle{4\over{16}}}{\text{ pounds}}}} = {{\$ 7.14} \over
{5.25{\text{ pounds}}}} = \$ 1.36{\text{ per pound}}$

Note that there are 16 ounces in a pound, so 5 pounds and 4 ounces is equal to $5{4 \over {16}}$ or 5.25 pounds.

Example 4: Tip
If
you are calculating the actual amount you will pay for a product, round
your answer to two decimal places because you cannot pay a fraction of
a cent. When comparing unit prices, it is okay to keep more than two
decimal places because you want to have an accurate comparison.