Question

The cost of 2.5 pounds of cheese is $5.60. Mrs. Peterson bought 9 pounds of cheese for her deli. How much money did Mrs. Peterson spend?

Answer 1

`color(green)($20.16`

Explanation:

We want the cost to weight ratio to be the same.

That is we want the price of `9` pounds (lets call it `$x`) to be such that

`$5.60 : 2.5 " pounds"` is the same as `$x : 9 " pounds"`

or written as fractions, we want
`($5.60)/(2.5" pounds")=($x)/(9" pounds")`

That is
`color(white)("XXX")$x = ($5.60)/(2.5cancel(" pounds"))xx9cancel(" pounds")`

`color(white)("XXXXX")=($50.40)/(2.5) = $20.16`