### Home > CC3MN > Chapter 4 > Lesson 4.1.3 > Problem4-29

4-29.

Joe drove $100$ miles from San Francisco to Gilroy and used $4$ gallons of gas.  How much gas should he expect to use for a $3000$-mile trip to New York City?  What is the unit rate (miles per gallon)?  Be sure to justify your reasoning.

Set up a proportion with the information in the problem.

$\frac{\text{miles}}{\text{gallons}}=\frac{100}{4}=\frac{3000}{x}$

$\text{Solve for }x.$

$4\left(\frac{100}{4}\right)=\left(\frac{3000}{x}\right)4$

$x(100)=\left(\frac{12000}{x}\right)x$

$100x = 12000$

$x=120$ gallons