IXL | Write equations for proportional relationships from graphs

Gabby is throwing a pool party to kick off the summer. Her pool is empty, so she starts filling it with water from a garden hose.

There is a proportional relationship between the time Gabby has been filling up the pool (in minutes),

and the volume of water in the pool (in gallons),

Write an equation for the relationship between x and

Simplify any fractions.

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Learn with an example

Sanjay is making his special punch for the Starry Night homecoming dance.

There is a proportional relationship between the number of cans of peach juice concentrate in a punch bowl,

and the corresponding number of bottles of lemon-lime soda,

Write an equation for the relationship between x and

Simplify any fractions.

The graph of a proportional relationship is a straight line passing through the origin

(

)

A proportional relationship between x and y can be modeled by the equation

The letter k is the constant ratio of y to

It is called the constant of proportionality.

To write an equation for the relationship between x and

first find the constant of proportionality. Start by identifying the coordinates of one of the points on the line.

Calculate the ratio of the

y-coordinate

to the

x-coordinate.

The constant of proportionality is 1 bottle of lemon-lime soda per can of peach juice concentrate.

Since the product 1x is commonly written without the 1, an equation for the relationship is:

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