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# Identifying constant of proportionality graphically

The video explains the concept of the constant of proportionality in graphs. It shows how to calculate it using the formula Y = KX or Y/X = K, where K is the constant. It also demonstrates how to identify lines with specific constants on a graph.

## 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 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.
• 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!
• why dont i get thisbut everyone else does
• You'll get it eventually!
• 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.
• This makes no sence ahhhh
• i didnt understand anything,

My brain nearly exploded
• for rreal
(1 vote)
• I know we normally use y=kx equation but is there a reason to use ky=x instead? Also how would you know when to use each equation?
• we do not use ky=x instead because it is incorrect. But if you mean y/k=x or y/x=k, which is correct, and we sometimes use it because we feel like it and it is another way of solving constant of proportionality.
• This is a little bit confusing, esxpecially the 1st example.
• Can someone help me?

We can calculate E, the amount of euros that has the same value as D U.S. dollars, using the equation E = 17/20 D

How many euros have the same value as 1 U.S. dollar?

How many U.S. dollars have the same value as 1 euro?