Question

John drove 48 miles and used 2 gallons of gasoline. How many gallons of gasoline will he use if he drives 78 miles?

Answer 1

`3.25" gallons"`

Explanation:

The ratio of gasoline used to miles drive is (assumed to be) constant.

So if `color(blue)x` gallons are the amount required to drive `78` miles, then
`color(white)("XXX")(color(blue)x" gallons")/(78" miles")=(2" gallons")/(48" miles")`

`color(white)("XXX")rArr color(blue)x" gallons"=(2" gallons")/(48cancel("miles"))xx(78cancel(" miles"))/color(white)1`

`color(white)("XXXXXXXXXXX")=78/24" gallons" = 3.25" gallons"`