1. Proportions

Just a couple of simple questions I'm having trouble on.

6. y is directly proportional to the square of x, and y = 48 when x = 4. What is y when x = 24?

10. y is inversely proportional to x, and y = 32 when x = 4. what is y when x = 18?

Thanks.

2. Originally Posted by PandaPanda
Just a couple of simple questions I'm having trouble on.

6. y is directly proportional to the square of x, and y = 48 when x = 4. What is y when x = 24?

10. y is inversely proportional to x, and y = 32 when x = 4. what is y when x = 18?

Thanks.

$y=cx^2$

$48=16c$

$c=3$

$y(24)=3*24^2$

3. Originally Posted by PandaPanda
Just a couple of simple questions I'm having trouble on.

6. y is directly proportional to the square of x, and y = 48 when x = 4. What is y when x = 24?

10. y is inversely proportional to x, and y = 32 when x = 4. what is y when x = 18?

Thanks.
When something is directly proportional it means,
$y=kx$ where k is some constant.

Inversly proportional means,
$y=\frac{k}{x}$

so if y is directly proportional to the square of x then,
$y=kx^2$

Then use your values given to solve for K.

Hope that helps!

4. Thanks.

What confused me was there were problems stating "y varies directly/inversely with x" and "y is directly/inversely proportional to x"

What's the difference?

5. Originally Posted by PandaPanda
Thanks.

What confused me was there were problems stating "y varies directly/inversely with x" and "y is directly/inversely proportional to x"

What's the difference?

Are you still needing to know the difference, or did I make it clear enough in my last post?