IXL | Find the constant of proportionality from a table: with decimals

As a farmer, Judith keeps a close eye on the weather. After a few stressful weeks with no rain, Judith was relieved when it started raining one morning. It rained steadily all day, and Judith periodically checked to see how much rain had fallen.

There is a proportional relationship between the amount of time (in hours) it had been raining,

and the amount of rain (in inches) that had fallen,

x (hours)	y (inches)
2	0.5
4	1
8	2
12	3

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

inches per hour

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Learn with an example

question

Daniel is throwing a pool party to kick off the summer. His pool is empty, so he starts filling it with water from a garden hose.

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

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

x (minutes)	y (gallons)
0.6	9
0.8	12
0.9	13.5
1	15

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

gallons per minute

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 (minutes)	y (gallons)	Ratio of y to x (gallons per minute)
0.6	9	9 0.6 = 15
0.8	12	12 0.8 = 15
0.9	13.5	13.5 0.9 = 15
1	15	15 1 = 15

The ratio for each pair of

and

y-values

15.

So, the variables have a proportional relationship.

So, the constant of proportionality is 15 gallons per minute.

Looking for more? Try these:

Lesson: Proportional relationships

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