A Matrices Question

[WattZ]

Hey guys,

Well I've somewhat hit a bump. I was doing a 2011 Trial exam from NEAP and this question popped up, at first I thought that C was non existent, but then I noticed the next part relates to it and their is an actual answer to it in the solutions, but it was quite vague as NEAP often is. Can anybody work it out and put it in working here? it's attached and It's part c. Thanks.

[Bozo]

Question, I was forced to do Networks at school but its really shitting me. Should i do Matrices? FYI I am a methods student. Is the Matrices in further much different?

[WattZ]

Well I did 1 & 2 Methods and the Matrices section looks pretty similar only that methods is harder. It's usually an easy section and it's only 1 chapter so it's quite easy to learn if you have experience with matrices.

[iroflmfao]

Quite interesting.

If P is that 3X1 matices, then an inverse cannot exist.

Hmm Do you have solutions ?

[iroflmfao]

C has to be a 3 by 3.

THis is a hunch but  [0.8, 1.6,0;0.5,0,1;0,0,2} = c

[WattZ]

yeah, the solution for c is attached below now. Unfortunately NEAP are vague.

[tea.squaredd]

D is a 3x1 matrix.
P is a 3x1 matrix.
Thus C has to be a 3x3 matrix.
as D = CP
3x1 = 3x3  x  3x 1.

Now to work out what's within the matrix:
Since you are buying TWO shirts at 80% each, R1C1 is 1.6.
r1c2, is 0.8, as you are buying 1 business shirt at 23$.
r1c3, is 0, as 0 formal shirts are relevant in this deal.

r2c1 is 0.5 of the price, hence r2c1 is 0.5.
r2c2 is 0, as business shirts are irrelevant in this deal.
r2c3 is 1, as you are buying a formal shirt at the full price.

r3c1 is 0 as standard shirts are irrelevant.
r3c2 is 0 as you are getting the business shirt for FREE.
r3c3 is 2 as you are buying 2 formal shirts at full price.

therefore matrix C :       1.6  0.8  0
                                       0.5  0    1
                                       0     0    2

Hope this helps.

Edit: r1c1 = row 1, column 1   which refers to 1.6
as I'm sure you guys all know (:

[WattZ]

thanks, I appreciate it. I first tried the inverse, but after it failed and then it wasn't non-existent I was lost, being it a worded question didn't make it any easier.

[iroflmfao]

oh yea i got mixed up with the order of the top line.

Good question but, never came across that before.

[becexohex]

Hi are you able to post the answers, just the multiple choice letters