D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
Maths exam discussion - share revision tips in preparation for GCSE, A Level and other maths exams and discuss how they went afterwards.
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D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POSTD1 May 2012
Slighlty more challenging than normal paper.
Q1 - Fairly standard bin packing and bubble sort
(you do not need to show the waste, you normally do need a final pass)
Q2 - Very easy matchings
(there are other solutions)
Q3 - Standard Kruskal's / Prim's
Q4 - Postie - Quite tricky
Now Added
Valency - The number of arcs attached to a node.
There were no sneaky parts to the pairings; I think the totals were 205, 206 and 280ish
In part b) unusually you discounted HI making H and I even; therefore; you traverse the other (remaining) odd pairing twice to solve the problem.
However, you must remember to subtract HI from the original weight!
In part c) you would start at one of the odd nodes and end at the other; the length would be the original total weight - HI
Q5 - Tricky(ish) Dijkstra's
part c) will cause problems.
Q6 - Standard CPA but then a scheduling for the first time in 5 years.
I think the scheduling will be a total bloodbath, many students will not even know what it is.
If you drew a Gantt correctly you would get 1/4
Q7 - Linear Programming
Fairly tricky question; you DIDN'T need to test the integer points around V, you could have read the result directly from the graph.
I am going to guess the following boundaries
75 - 100ums
68 - 90ums
61 - 80ums
54 - 70ums
47 - 60ums
40 - 50ums
33 - 40ums
I will do my best to answer questions about the paper but please try to read the thread first so that I am not answering the same questions lots of times.
Here are some links to previous D1 threads, they are worth a read and you will see what the common errors were...
Pre-Exam Thread - http://www.thestudentroom.co.uk/show....php?t=1865487
This has loads of past papers, mark schemes, model solutions etc
Jan 2012 - http://www.thestudentroom.co.uk/show....php?t=1900076Last edited by Arsey; 20-05-2012 at 13:54. -
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Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POSTI thought the paper was good, although I did mess up 2 marks on route inspection, and most likely got the wrong optimal point for Linear Programming.
Hopefully the grade boundaries are low.Last edited by isp; 19-05-2012 at 00:37. -
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Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POSTI know where I lost my marks
Wasnt able to algebraicly solve the constraint y>5x or something like that ...
For some reason or another ... Instead of drawing y>5x .. i drew y>6x ... (dont ask)
For the route inspection where they cut the arc I forgot to minus the arc value from the total ...
Cant seem to think of anything else
Still an A?! D:
Edit: Oh and did what wangok did above
Still an A?... Damn it ...Last edited by shooby_doo; 19-05-2012 at 00:10. -
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Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POSTHoly guacamole!(Original post by wangok)
i did a Gantt Diagram instead of a schedule for that 4 marker! :'( Peak times blud x
Same ... ok need to redit my previous post .. -
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Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POSTHow do you know integer values weren't required? Doesn't make sense to make 42.6 cars... If you found the closest integervvalue and stated the profit based on that, think you'd get full marks (for the record I got (42, 20) )
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Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POSTDo the following values for the route inspection question (4) sound familiar to anyone?
4.
b) total length = 1436 + 205 = 1641
d) new length, 1492
e) without HI: 1436 - 75 = 1361
Also for Q1, is stating how much waste there is a requirement for full marks? Apart from that everything was ok
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Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POSTMy optimal point was (27,28), not sure what I did haha(Original post by isp)
Arsey for the Linear Programming problem, would I lose marks if I tested the top vertex which had pont (27, 27)?
I only tested three vertex's at different corners and for my maximising profit I got (50, 8) instead of (48, 10). Although on my graph I made (27, 27) the optimal point for some odd reason, and forgot to cross it out and change it.
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Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POSTYep, that's exactly what I got. I don't think so!(Original post by Dreamweaver)
Do the following values for the route inspection question (4) sound familiar to anyone?
4.
b) total length = 1436 + 205 = 1641
d) new length, 1492
e) without HI: 1436 - 75 = 1361
Also for Q1, is stating how much waste there is a requirement for full marks? Apart from that everything was ok
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Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POSTlol, I am on fire(Original post by isp)
Scheduling came up today aswell...
C2 people - expect a big wordy geometric, prob with logs, maybe even proof of the series. -
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Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POSTof course integer values are required. Why do you think they weren't?(Original post by lukas1051)
How do you know integer values weren't required? Doesn't make sense to make 42.6 cars... If you found the closest integervvalue and stated the profit based on that, think you'd get full marks (for the record I got (42, 20) ) -
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Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POSTDo you think there's other possible answers for the schedualing? the activities had massive float, like E F and D so I just kind of arranged them into 3 workers and it seemed to work but isnt the what you have given in the mark scheme...thanks x
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Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST(Original post by Dreamweaver)
Do the following values for the route inspection question (4) sound familiar to anyone?
4.
b) total length = 1436 + 205 = 1641
d) new length, 1492
e) without HI: 1436 - 75 = 1361
Also for Q1, is stating how much waste there is a requirement for full marks? Apart from that everything was ok
no need for waste, just helps to spot silly numerical errors.
those numbers do sound familiar. On the last part you had to write out the route. -
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Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POSTHow many point do you think I'd lose for using the minimising point rather than maximising?(Original post by Arsey)
lol, I am on fire -
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Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POSTyes, there will be lots of possible answers; very daft question I thought; if they were going to give a scheduling at least make it a challenging one.(Original post by itssochaotic)
Do you think there's other possible answers for the schedualing? the activities had massive float, like E F and D so I just kind of arranged them into 3 workers and it seemed to work but isnt the what you have given in the mark scheme...thanks x -
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Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POSTYep, doesn't matter as long as you use 3 workers and finish in the critical time. (I checked this as soon as I got out - I wasn't sure either!)(Original post by itssochaotic)
Do you think there's other possible answers for the schedualing? the activities had massive float, like E F and D so I just kind of arranged them into 3 workers and it seemed to work but isnt the what you have given in the mark scheme...thanks x
