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# FP1, random question, something with ratios I think? watch

1. http://www.suffolkmaths.co.uk/pages/...02009%20QP.PDF

Question 7, a)

The way I'm looking at it is with ratios. 'r' lies a certain distance from a, and b.

Distance 'ab' = b - a.

Ratio of r from a : ratio of r from b

= r - a : b - r

So, if you multiply the distance 'ab' by the ratio of r from a, and add a, you should find r?

Then I'd consider the ratio in terms of c and d and get some other stuff.

I dunno if I'm going along the right lines here or if I'm completely wrong.
2. (Original post by ebmaj7)
[

I'm not sure what you're doing with "ratio of r from a", but am somewhat wary, since a ratio is a relationship between two things, and the ratio 1:2 is the same as 2:4, so to use just one part of it by itself doesn't seem right.

Additionally your equation reduces to r=r, which doesn't get you anywhere.

What I'd do is:

Work out the gradient of the straight line in terms of a,b,c,d.

Then express the y co-ordinate or r (which is 0) in terms of c + the distance between a and r times the gradient; be careful with signs.
3. (Original post by ghostwalker)
I'm not sure what you're doing with "ratio of r from a", but am somewhat wary, since a ratio is a relationship between two things, and the ratio 1:2 is the same as 2:4, so to use just one part of it by itself doesn't seem right.

Additionally your equation reduces to r=r, which doesn't get you anywhere.

What I'd do is:

Work out the gradient of the straight line in terms of a,b,c,d.

Then express the y co-ordinate or r (which is 0) in terms of c + the distance between a and r times the gradient; be careful with signs.
Okay.

Gradient = (c - d) / (b - a)

Hmm, should be + c...

That's annoying.
4. (Original post by ebmaj7)
Gradient = (c - d) / (b - a)

Hmm, should be + c...

That's annoying.
That's because you got the gradient wrong.

Gradient = (d - c) / (b - a)

The first terms (d,b) top and bottom, refer to Q, and the others refer to P.
5. (Original post by ghostwalker)
That's because you got the gradient wrong.

Gradient = (d - c) / (b - a)

The first terms (d,b) top and bottom, refer to Q, and the others refer to P.
Ah right, yes.

Okay, thankyou muchly.

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