How can you use a rate to compare the costs of two boxes of cereal that are different sizes?

Price of box of cereal #1
---------------------------- = $ per ounce(or other unit)
Size of box #1 (in ounces,
or some other unit)

Price of box of cereal #2
---------------------------- = $ per ounce(or other unit)
Size of box #2 (in ounces,
or some other unit)

Whichever has the smaller answer (the cost is the least per ounce) is the best deal.

Answer Link

calculista calculista · Answer 2 · 2018-08-03T10:42:42-04:00

Let

a1----------> price of box of cereal #[tex] 1 [/tex]

b1----------> price of box of cereal #[tex] 2 [/tex]

a2---------> size of box #[tex] 1 [/tex] (in ounces,grams or some other unit)

b2---------> size of box #[tex] 2 [/tex] (in ounces,grams or some other unit)

we know that

A rate is a comparison of two quantities that have different units

So

Step 1

Find the rate of the box of cereal #[tex] 1 [/tex]

[tex] rate1=\frac{a1}{a2}\frac{usd}{unit} [/tex]

Step 2

Find the rate of the box of cereal #[tex] 2 [/tex]

[tex] rate2=\frac{b1}{b2}\frac{usd}{unit} [/tex]

Step 3

Compare the rates

Whichever has the smaller rate is the best deal.

remember, to be able to compare both cereal boxes they must have the same unit of measure (grams with grams, ounces with ounces, etc.)