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# Identifying constant of proportionality graphically

Sal identifies the constant of proportionality from a line graphed on a coordinate plane.

## Want to join the conversation?

• I'm confused at the constant of proportionality
• The constant of proportionality is what determines the relationship between y and x. If r is the constant of proportionality then an example is y = rx . The value of y is dependant on how the given value of x is effected by the constant of proportionality.
• why dont i get thisbut everyone else does
• Let's be honest here.
When do you use this in life??

• Real world examples of proportionality constants are speeds (for example miles per hour), densities (for example grams per milliliter), prices per unit bought, and hourly pay rates.

Have a blessed, wonderful day!
• who and y did they put letters in math >:(
• Why did you use a k and not a c to represent constant?
• Nobody knows for sure why. But it is strongly believed that k is used as constant almost everywhere, because the German word for ‘constant’ is ‘konstante’. The first letter of that word is k. And the Germans contributed in mathematics hugely since the dawn of it.
While c is used for many other tasks and usually is not available.
• When Sal said y=x, does that mean that any point on the line for y or x, will equal each other?
• Yes. For any point on the line y = x, the x and y of the point will equal each other.
• I will just click the 'Up Next' button, and if I am asked any questions, I will press the first thing I see, and pray with all my might that I got it at least half right...
• me to
(1 vote)
• what is this? I don’t understand
• The graph of a proportionality relationship is always a straight line through the origin. To find the proportionality constant, pick any point on the line (other than the origin) where you can easily read the coordinates, and divide the y-coordinate by the x-coordinate. Then you might want to check your answer by doing the same calculation with another point on the line (other than the origin).

It probably won’t be long before you start learning about slope (a measure of the steepness of a line). In the graph of any proportionality relationship, the proportionality constant is the slope of the line!

Have a blessed, wonderful day!