Using Direct Variation to Solve Application Problems, Part 2

1.15.4 Using Direct Variation to Solve Application Problems, Part 2

1.15.4 • Using Direct Variation to Solve Application Problems, Part 2

Cool Down

Jesse’s car gets 30 miles per gallon of gas.

Write an equation using direct variation for distance, $d$ , and number of gallons of gas, $g$ for this problem.

Compare your answer:

Use the equation for direct variation $y = k x$ . So, $d = k g$ .

If Jesse travels 150 miles he uses 5 gallons of gas. Find the constant of variation.

Compare your answer:

Use the equation for direct variation $y = k x$ . So, $150 = k (5)$ . The constant of variation is $k = 30$ .

Now, write the equation if Jesse travels $d$ miles with a car that uses 30 miles per gallon of gas.

Compare your answer:

$d = 30 g$

If Las Vegas is 285 miles away, how many gallons of gas are needed to get there?

Compare your answer:

Substitute 285 miles in for $d$ in the equation. So, $285 = 30 g$ and $g = 9.5$ .

Why Should I Care?

A woman and a young girl smile while holding a piggy bank together, as seen on a tablet screen held by a hand. The background includes a kitchen with warm lighting and a brick wall.

Alex's mother can use algebra to budget her paycheck from her job as an accountant. She uses some money for food, rent, medicine, and things like water and electricity.

If she uses variables to represent the different ways that she uses her money, she can put those variables into an equation to make sure she has enough money to pay for all those things.