Example Question #1 : Proportional Relationships
An electronics store is having a sale and offering off the regular prices of all laptop computers. If the sale price for a certain laptop is , what is the regular price of the laptop?
Notice that is the price after the discount. Therefore, the sale price of is of the regular price (or times the regular price). The regular price can be represented as , or times the regular price.
First, set up a proportion describing the problem, using to represent the unknown quantity, the regular price:
Next, cross multiply:
Finally, divide both sides by to solve for :
Therefore, the regular price is .
Example Question #2 : Proportional Relationships
3 sticks of butter weigh 12 ounces combined. Using this information, determine the weight of 7 sticks of butter.
Set up a proportional relationship, using to represent the unknown quantity (the weight of 7 sticks of butter):
Finally, divide both sides to solve for :
Example Question #3 : Proportional Relationships
If is inversely related to and and is directly related to , which formula describes the relationship between and ?
To say that is inversely related to is to say .
To say that is directly related to is to say .
Thus, to say is inversely related to and and is directly related to is to say