# Thread: Finding the formula to an inversely proportional formula?

1. ## Finding the formula to an inversely proportional formula?

Suppose y is inversely proportional to x. If y = 6 when x = 4, find the constant of proportionality and write the formula for y as a function of x. Use your formula to find x when y = 8.

I know that the inversely proportional formula is y = (k)/(x^n) or kx^-n. But how would we find the formula to this problem? They only gave us one set of coordinates, (4,6) and when we plug in those values for x and y what should we be solving for? Because there would be two unknown values we don't know which is -n and k. Please help me with this problem, thank you.

2. Originally Posted by florx
Suppose y is inversely proportional to x. If y = 6 when x = 4, find the constant of proportionality and write the formula for y as a function of x. Use your formula to find x when y = 8.

I know that the inversely proportional formula is y = (k)/(x^n) or kx^-n. But how would we find the formula to this problem? They only gave us one set of coordinates, (4,6) and when we plug in those values for x and y what should we be solving for? Because there would be two unknown values we don't know which is -n and k. Please help me with this problem, thank you.
You have been told that y is inversely proportional to x.

So you have:

$y = \frac{k}{x}$ : inversely proportional to x. So, find k!

If y was directly proportional to x,then $y = kx$