Maths help!!

Editorry wrong post

Hi I was wondering if anyone would be able to help me with a homework question:

P, Q and R have positive values.
P is directly proportional to the square of Q.
When P = 1.25, Q = 0.5
Q is inversely proportional to R.
When Q = 0.5, R = 6
Work out the value of R when P = 0.8

It’s probably really easy but idk where to start
Thanks in advance

So when something is directly proportional how can we write that in an equation?

I think it’s y = kx but I don’t really understand what the k means

K is a constant -a multiplier that shows the relationship between the two values.

So you know that P is directly proportional to the square of Q -how would you write that?

P = kQ² ? Idk

Yup that’s it.
Now use the values they give you
“When P=1.25, Q=0.5”
and put them into that equation to work out the value of k

Okay so 1.25 = 0.25 x k
1.25 / 0.25 = 5
K = 5 ?

👍🏼 now you can rewrite your formula for p and q using that value for k.

Now how do we write when something is inversely proportional?

y = k / x

Excellent, now the question tells you that Q is inversely proportional to R.
Once you’ve written that equation, sub in the value the question gives you to find out k for this one.

0.5 = k / 6
k = 3

Fab so you should now have two equations

One connecting P and Q and the other connecting Q and R

I think this is wrong
P = 5Q²
Q = 3 / R

Why do you think it’s wrong?

I’m not sure it was just a guess

well it’s correct you worked out k and then you put those values back into the equations for proportional relations.

now you have those two equations, can you finish off the question?

0.8 = 5q²
q = 0.4
0.4 = 3 / r
r = 7.5 ?