D1 Jan 2012 Edexcel Post-Exam Discussion - Solutions and paper in first post

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JOR2010

how did u find it??? think i done terrible how how come in increase i thought decrase!

Other than the postman question, I think I did fine. But it didn't specify a start/end node, so the minimum length is surely when the graph is made semi-eulerian, and the two remaining odd nodes are the start/finish nodes?

Reply 41

otrivine

Original post by JOR2010

i got drew the correct lines and did the correct working but i labelled the feasible wrong how many marks wil i lose/

Reply 42

bethany18

Original post by bethany18

for some reason for 2a that C had an odd valency(dont know what i was thinking), will i lose all marks for that question or still get 1 or something for doing the correct working out?

Also i didnt include C in my critical path for the last one but did F and I, do i lose all marks for that?

Reply 43

JOR2010

Original post by Arsey

not sure, 60+ for an A.

definitions are normally terribly answered, as will the dummy questions.

I think the postie question will be a bloodbath too.

LP was pretty kind.

Surely Edexcel MUST allow more than one answer for the postie question, as no start/end node was specified, and therefore (you even said yourself), the minimum route is shorter when you start and finish at an end node.
I mean, i got the answer to be 139 miles, which is shorter than your answer, starting/finishing at E/F and repeating the arc, weight 10.

(edited 12 years ago)

Reply 44

fruktas

For the second dummy, isnt the fact that J is dependent on G and H a perfectly valid reason?

Reply 45

JOR2010

Original post by otrivine

i got drew the correct lines and did the correct working but i labelled the feasible wrong how many marks wil i lose/

probably 1.

Reply 46

benji12394

i drew a profit line of 60x + 20y = 1200. is that ok?

Reply 47

benji12394

also for the lower bound of workers i did 22/8 and therefore got the right answer, 3. will i get the marks?

Reply 48

pepeeglesfield

Original post by JOR2010

But the route inspection did NOT specify a start node, surely the shortest path was starting at E/F, and adding the arc worth 10 to the tree? (EG SEMI-EULERIAN?)

YESSS!!!thats exactly what i thought. i re read the question and realised there was no start node specified so i just made it semi eularian giving the shortest route...how can that be wrong!

Reply 49

username916760

yeee. thats right mate

Reply 50

nekom241

Hi,
Just want to ask something for the question on matchings. Did we have to draw the improved and maximum matching on the 2 figures in the answer booklet?? I listed which node joins to which but I just realised I didn't draw it on the figures. So am I gonna lose any marks for not drawing it even though I stated which vertex joins to which. Thanks.

(edited 12 years ago)

Reply 51

JOR2010

Original post by pepeeglesfield

YESSS!!!thats exactly what i thought. i re read the question and realised there was no start node specified so i just made it semi eularian giving the shortest route...how can that be wrong!

Exactly, I find it weird that Arsey says it's the other one, I've mailed Edexcel, and hope Arsey will think both will be okay. I mean, my path turned out to be 139 miles, which is less than Arsey's! What did you get?

Reply 52

RG1994

For the chinese postman question, as it didn't specify that you must start and finish at the same vertice, i only traversed the shortest distance between two vertices with odd valencies. So i disagree with the solution in the paper, surely you cannot assume that you must start and finsih at the same vertice if it doesn't specify?

Reply 53

JOR2010

Original post by RG1994

Exactly, there are quite a few of us here who have done that, and we're right, and those who did the usual doubling of path between 4 odd nodes are technically wrong!

Reply 54

.Username.

To get the route inspection problem right you had to add the shortest length of the two nodes which were not part of the canal, with the original length + canal length, as they required you to start and finish at the same node, i dont see why people added only the canal as this would make the graph only Semi-Eulerian

Reply 55

username916760

is there anyone who has found the markscheme for physics??????

Reply 56

robert jones

Original post by JOR2010

edexcel d1 page 67: route inspection (Chinese postman) algorithm can be used to find the shortest route that traverses every arc atleast once and returns to the starting point.

(edited 12 years ago)

Reply 57

Prolite

Original post by otrivine

for dijkastras i got 115?

I got 115 tooo??

dang man

I am defo getting U in this paper

Reply 58

hellomoto170

I got 149 for prims and kruskals but I don't know if it was a calculator error as in I typed in the wrong digit or if I selected the wrong edges... How many marks would I lose for getting 149 instead of 148? And how many marks would I lose for getting 115 in djikstras for part A)? I also did 115 for B) but would I get most marks as method marks for A)?