IXL | Find the constant of proportionality from a table

Steve loves to play the piano but doesn't like practicing the exercises his piano teacher assigns. Steve knows the exercises will help him play better though, so he tries to motivate himself using his favorite treat—chocolate chip cookies.

There is a proportional relationship between the amount of time (in hours) that Steve practices the piano,

and how many cookies he gives himself,

x (hours)	y (cookies)
2	4
3	6
4	8
5	10

What is the constant of proportionality? Write your answer as a whole number or decimal.

cookies per hour

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Learn with an example

question

Kenny's class is having a holiday party, and he is in charge of bringing juice. He decides to bring powdered juice mix and add water to it at school.

There is a proportional relationship between the volume of water Kenny uses to make the juice (in liters),

and the number of scoops of juice mix he uses,

x (liters)	y (scoops)
5	10
6	12
7	14
8	16

What is the constant of proportionality? Write your answer as a whole number or decimal.

scoops per liter

key idea

Two variables have a proportional relationship if the ratio of one variable to the other is constant.

If x and y have a proportional relationship, the constant of proportionality is the ratio of y to

solution

To find the constant of proportionality, calculate the ratio of y to

x (liters)	y (scoops)	Ratio of y to x (scoops per liter)
5	10	10 5 = 2
6	12	12 6 = 2
7	14	14 7 = 2
8	16	16 8 = 2

The ratio for each pair of

and

y-values

So, the variables have a proportional relationship.

So, the constant of proportionality is 2 scoops per liter.

Looking for more? Try these:

Lesson: Proportional relationships

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