Two values that are proportional to one another may be directly or inversely related (also known as direct variation and inverse variation). Later on, you will learn the equations for calculating direct and inverse variation; however, this lesson will instead focus on the meaning of direct and inverse and how to differentiate the two.
So what is direct variation? Well, imagine you get a job working as a babysitter, and you get paid $15 for every hour you babysit. In that case, the amount of money you earn is directly proportional to how many hours you work. If you babysit for 2 hours, you earn $30, and if you work for 3 hours, you earn $45.
Thus, your payment is directly proportional to the number of hours worked. In other words, as hours worked increases, payment increases at the same rate.
As you may have guessed, inverse variation is the opposite of direct variation. This occurs when increasing one value decreases the other value at a constant rate. For example, imagine you are on a road trip with your parents. You may have to travel very far from one place to another, maybe even hundreds of miles. If your mom does the driving, and she prefers to drive fast, then the time it takes you to reach your destination will decrease. If your dad drives and he prefers to drive slowly, then the time it takes you to reach your destination will increase.
Therefore, you could say that speed and travel time are inversely proportional. The faster the car moves, the less time it takes to travel from point A to point B.
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