Question

Find the constant of proportionality.

Answer 1

Answer as a fraction =  4/3

Answer in decimal form = 1.33 approximately

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Explanation:

x = number of days

y = number of inches

For instance, on day x = 3, we have y = 4 inches of flood water. This is shown by the point (x,y) = (3,4) on the diagonal line.

Divide y over x to get the value of k, which is the constant of proportionality.

k = y/x

k = 4/3

k = 1.33 which is approximate

You could also pick a point like (x,y)  = (6,8) to find that

k = y/x

k = 8/6

k = 4/3

k = 1.33

Which is the same as earlier.

We can pick any point on the diagonal line as long as it's not the origin point (0,0).

The equation of this direct variation line is y = (4/3)x. It has a slope of 4/3 and a y intercept of 0. The slope of 4/3 means that each time we move up 4 on the y axis, we move to the right 3 units on the x axis.

In short, slope = rise/run = 4/3. So rise = 4 and run = 3.

For any direct variation linear equation, the slope and constant of proportionality are the same thing.