Direct Variation Models (11:11)
 Describe direct variation.
 What is the formula for direct variation? What does
k represent?
Translate the following direct variation situations into equations. Choose appropriate letters to represent the varying quantities.
 The amount of money you earn is directly proportional to the number of hours you work.
 The weight of an object on the Moon varies directly with its weight on Earth.
 The volume of a gas is directly proportional to its temperature in Kelvin.
 The number of people served varies directly with the amount of ground meat used to make burgers.
 The amount of a purchase varies directly with the number of pounds of peaches.
Explain why each equation is not an example of direct variation.

4x=y 
y=9 
x=−3.5 
y=18x+7 
4x+3y=1