# Maths help!!

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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

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

Last edited by 67824930; 1 month ago

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#2

Editorry wrong post

Did you change your question??

Did you change your question??

Last edited by GabiAbi84; 1 month ago

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(Original post by

Editorry wrong post

**GabiAbi84**)Editorry wrong post

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#4

(Original post by

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

**67824930**)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

Last edited by GabiAbi84; 1 month ago

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(Original post by

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

**GabiAbi84**)So when something is directly proportional how can we write that in an equation?

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#6

(Original post by

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

**67824930**)I think it’s y = kx but I don’t really understand what the k means

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

Last edited by GabiAbi84; 1 month ago

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(Original post by

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?

**GabiAbi84**)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?

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#8

(Original post by

P = kQ² ? Idk

**67824930**)P = kQ² ? Idk

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

Last edited by GabiAbi84; 1 month ago

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(Original post by

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

**GabiAbi84**)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

1.25 / 0.25 = 5

K = 5 ?

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#10

Now how do we write when something is inversely proportional?

Last edited by GabiAbi84; 1 month ago

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(Original post by

👍🏼 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?

**GabiAbi84**)👍🏼 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?

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#12

(Original post by

y = k / x

**67824930**)y = k / x

Once you’ve written that equation, sub in the value the question gives you to find out k for this one.

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(Original post by

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.

**GabiAbi84**)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.

k = 3

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#14

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

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(Original post by

Fab so you should now have two equations

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

**GabiAbi84**)Fab so you should now have two equations

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

P = 5Q²

Q = 3 / R

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(Original post by

Why do you think it’s wrong?

**GabiAbi84**)Why do you think it’s wrong?

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#18

(Original post by

I’m not sure it was just a guess

**67824930**)I’m not sure it was just a guess

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

Last edited by GabiAbi84; 1 month ago

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(Original post by

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?

**gabiabi84**)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?

q = 0.4

0.4 = 3 / r

r = 7.5 ?

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