Question

A car travels 172 miles using 7 gallons of gas. At that rate, how far can the car travel using 42 gallons of gas?

Answer 1

You could do this as a proportion problem, or as a rate problem.

Proportion:
\[\frac{172 \text{ miles}}{7 \text{ gallons}} = \frac{x \text{ miles}}{42 \text{ gallons}}\]Cross-multiply to get \[172*42 = 7*x\]\[x = \text{ ?}\]

As a rate:
\[172 \text{ miles} / 7 \text{ gallons} \approx 24.6 \text { miles/gallon}\]
Distance = rate * fuel
\[D = 24.6 \text{ miles/gallon} * 42 \text{ gallon} = \]