Question

A 30 - ounce jar of salad dressing cost $ 2.39. A 3r - ounce jar costs $ 2.14, and a 13 - ounce jar cost $ 1.42. To the nearest cent, What is the cost per ounce of each size jar? Which is the best buy?

Answer 1

we can find the cost per ounce using cross multiplication

1.jar

`\begin{gathered} 30\longrightarrow2.39 \\ 1\longrightarrow x \end{gathered}`

where x is the cost per ounce

`\begin{gathered} x=(1*2.39)/(30) \\ x=0.079 \end{gathered}`

The cost per ounce is $0.08

2.Jar

`\begin{gathered} 24\longrightarrow2,14 \\ 1\longrightarrow y \end{gathered}`

where y is the cost per ounce

`\begin{gathered} y=(1*2,14)/(24) \\ y=0.089 \end{gathered}`

The cost per ounce is $0.09

3.Jar

`\begin{gathered} 13\longrightarrow1,42 \\ 1\longrightarrow z \end{gathered}`

where z is the cost per ounce

`\begin{gathered} z=(1*1,42)/(13) \\ z=0.109 \end{gathered}`

The cost per ounce is $0.11

the best buy is the first jar because it's cheaper per ounce