# Directly proportional?

1. Dec 14, 2004

### sotellme

directly proportional? can anyone give an example of it?

thanks alot!

2. Dec 14, 2004

### Pyrrhus

y and x are directly proportional, A is a constant.

$$y = Ax$$

$$\frac{y}{x} = A$$

3. Dec 14, 2004

### Sirus

Right. This is represented as $$y\propto x$$.

4. Dec 14, 2004

### sotellme

thanks!

5. Dec 14, 2004

### cyby

Careful. Make sure A is not a positive constant < 1. Otherwise you will get that they are inversely proportional.

6. Dec 14, 2004

### sotellme

hi cyby! what you mean with that? do you mean that A must always be a positve number if not it will be inversely proportional?

7. Dec 14, 2004

### Tom Mattson

Staff Emeritus
No, that's not true. It's still a direct proportion. y and x are inversely proportional if y=A/x.

8. Dec 14, 2004

### cyby

Uh, you are right. Sorry, was thinking about something else completely.