# Direct/Inverse proportion

hello

we have been covering direct and inverse proportion at school. Are there any other types of proprtion?

We've been coming across questions like:

x is directly proportion to Y

Then I've been told to write

X (the proportion sign, which is like 8 on its side) Y

X=ky

We are then given a value for x and a value for y and asked to work out k. I'm fine with that but I'm wondering why we have to put "k"? Why does that proportion sign turn into "K"?

Also i was looking at the friedmann equation and i saw it had a "k" in it. When i see a physics equation like that will the K usually mean "constant" and will it have something to do with proportion?

thanks _Muddy_

symbolipoint
Homework Helper
Gold Member
Any proportionality constant, if consistantly applied in the situation can be used; whether k, or c, or R, or K, or C, or anything which you can accept as a constant. Just understand that case-level really matters, so that k is a different number than K. x is a different number than X. Be consistant with your use of variables.

symbolipoint
Homework Helper