# URGENT D1 Completely Baffling Question!!!!!!! HELP

#1
Hey guys, this question has me totally stumped. How would you attempt part B of this question?

This is D1 June 2014 Edexcel.

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6 years ago
#2
(Original post by thebobby)
Hey guys, this question has me totally stumped. How would you attempt part B of this question?
First find the co-ordinates of A,B,C and D and substitute them into the equation p=x+ky.
You know that the value of P for A is < the value of P for D and so you can create and inequality and solve for one value of k.
You can create another inequality using the value of P for C is < the value of P for D, or another statement that is equally correct.
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#3
(Original post by Thinking_Aloud)
First find the co-ordinates of A,B,C and D and substitute them into the equation p=x+ky.
You know that the value of P for A is < the value of P for D and so you can create and inequality and solve for one value of k.
You can create another inequality using the value of P for C is < the value of P for D, or another statement that is equally correct.
Thank you so much for your answer. But how do you know to pair up A with D and C?

Also in the model answer they piar it up like this, why?

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6 years ago
#4
(Original post by thebobby)
Thank you so much for your answer. But how do you know to pair up A with D and C?

Also in the model answer they piar it up like this, why?

Honestly, I paired those up as they were the first pairings to occur to me, but I don't think it matters which two you pair up as long as the statement itself is correct.
In answer to your second question, I think its just because that is the simplest way to gain two different values for k and so find the range. They paired up A and B, and C and D, as you only know for a fact that D has the largest profit and A the smallest, therefore you cannot create an inequality between B and C as you don't know the size of their profits in relation to each other.
I'm sorry if my explanation isn't very clear- I'll try and reword it.
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#5
(Original post by Thinking_Aloud)
Honestly, I paired those up as they were the first pairings to occur to me, but I don't think it matters which two you pair up as long as the statement itself is correct.
In answer to your second question, I think its just because that is the simplest way to gain two different values for k and so find the range. They paired up A and B, and C and D, as you only know for a fact that D has the largest profit and A the smallest, therefore you cannot create an inequality between B and C as you don't know the size of their profits in relation to each other.
I'm sorry if my explanation isn't very clear- I'll try and reword it.
I see so are you saying its a bit of random pairing? It doesnt actually matter how I pair the coordinates up? I could compare say A with C and D with B? as this is what they have in the M/S.
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6 years ago
#6
(Original post by thebobby)
I see so are you saying its a bit of random pairing? It doesnt actually matter how I pair the coordinates up? I could compare say A with C and D with B? as this is what they have in the M/S.
Right, I've gone over my working from yesterday and I believe I was wrong to suggest it was a random pairing, sorry.
I believe you have to pair A and B, and C and D as a much broader range is produced when comparing A with C and D with B. I think this is because there is a larger difference between the profits and so a larger range of values k could take, however I cannot find an explanation anywhere.
I believe you would pair the points that would give the highest value for P and the two points that would give the lowest in order to gain the most accurate range for k.
I hope this helps, I'll carry on searching and see what I can find.
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