IXL | Find the constant of proportionality from tables and graphs

Jennifer has written her own recipe for pot roast.

There is a proportional relationship between the weight (in pounds) of the pot roast,

and the total cooking time (in hours),

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

hours per pound

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Learn with an example

question

Gina has outgrown the bike she rode when she was small. So, for her twelfth birthday, her parents surprise her with a five-speed Blaze Rider 2000! Gina has never had a bike with multiple speeds before, and she is eager to learn how it works. She starts by testing the middle speed.

There is a proportional relationship between the number of times Gina pedals,

and the number of times the wheels rotate,

x (times Gina pedals)	y (times the wheels rotate)
4	8
7	14
9	18
10	20

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

wheel rotations per time Gina pedals

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 (times Gina pedals)	y (times the wheels rotate)	Ratio of y to x (wheel rotations per time Gina pedals)
4	8	8 4 = 2
7	14	14 7 = 2
9	18	18 9 = 2
10	20	20 10 = 2

The ratio for each pair of

and

y-values

So, the variables have a proportional relationship.

So, the constant of proportionality is 2 wheel rotations per time Gina pedals.

Looking for more? Try these:

Lesson: Proportional relationships

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L.5Unit rates

W.8Rate of change: graphs

Lesson: Proportional relationships

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