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# 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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1. D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
D1 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

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

Here are some links to previous D1 threads, they are worth a read and you will see what the common errors were...

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=1900076
Attached Files
2. 12 May D1 RA4.pdf (856.8 KB, 3847 views)
3. Last edited by Arsey; 20-05-2012 at 14:54.
4. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
I 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 01:37.
5. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
solutions are in the first post
6. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
was a very simple paper but i didn't learn the line method on linear programming so lost 6 marks there but other than that it was fine at least I hope ...
7. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
i did a Gantt Diagram instead of a schedule for that 4 marker! :'( Peak times blud x
8. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
I 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 01:10.
9. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
(Original post by wangok)
i did a Gantt Diagram instead of a schedule for that 4 marker! :'( Peak times blud x
Holy guacamole!
Same ... ok need to redit my previous post ..
10. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
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) )
11. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
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
12. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
What u reckon the grade boundaries gonna be ma homies?!?!?!?!? x
13. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
(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.
My optimal point was (27,28), not sure what I did haha
14. 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
Yep, that's exactly what I got. I don't think so!
15. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
Question 4 missing!
16. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
(Original post by isp)
Scheduling came up today aswell...
lol, I am on fire

C2 people - expect a big wordy geometric, prob with logs, maybe even proof of the series.
17. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
(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) )
of course integer values are required. Why do you think they weren't?
18. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
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
19. 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.
20. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
(Original post by Arsey)
lol, I am on fire
How many point do you think I'd lose for using the minimising point rather than maximising?
21. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
(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
yes, 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.
22. Re: D1 May 2012 - Post Exam Thread - Paper and Solution in the FIRST POST
(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
Yep, 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!)

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