IXL | Find the constant of variation

This graph shows how the cost of a charity gala depends on the number of attendees.

$10

Cost

Attendees

Cost of a charity gala

What is the constant of variation?

$ per attendee

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Learn with an example

question

This graph shows how the total number of postcards Ariel buys is related to the number of days she spends on vacation.

100

Number of postcards bought

Days of vacation

Postcards Ariel has bought

What is the constant of variation?

Write your answer as a decimal or integer.

postcards per day

key idea

The constant of variation is equal to the slope.

slope

change in y

change in x

solution

Find any two points on the line.

100

Number of postcards bought

Days of vacation

Postcards Ariel has bought

Two points on the line are (0, 0) and (10, 50). Put those points into the slope formula.

slope

change in y

change in x

Plug in (0, 0) and (10, 50)

50 − 0

10 − 0

Plug in (0, 0) and (10, 50)

Subtract

Simplify

The slope is 5. The constant of variation is 5 postcards per day.

Looking for more? Try these:

Lesson: Constant of proportionality

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Not feeling ready yet? These can help:

N.4Find the constant of proportionality from a graph

N.1Find the constant of proportionality from a table

Lesson: Constant of proportionality

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