The Edexcel D1 (18/05/12 - AM) Revision Thread

Revision thread for the D1 exam.

I will upload the Jan 12 model answers on the day following the examination (Saturday morning!)

In the next few posts I will upload some past papers, mark schemes etc

Could you upload the mark schemes please and also June 2011 Answerbooklet +paper+ MS

thanks a lot!!!
your help is much appreciated!!!

So I'm just about to start teaching myself half the syllabus :/ does anyone know the grade boundaries for may 09 and may 10 papers? Also is it true jan papers have higher grade boundaries than te summer ones?

that was quick! lol

thanks so much!!!

btw i always seeem to get the scheduling questions wrong...is there more than one answer and how do you actually schedule workers?!

there is very likely to be more than one answer.

If you find scheduling hard, first pray it isn't on the exam tomorrow, but if it is... first draw out gantt chart. Scheduling is very easy if you have the Gantt drawn, just slide the activities into their floats until you find a solution that fits.

Can't wait to get this out of the way so I can do some real maths.

Well, I'm hoping not to make any of these mistakes anyway! Do you know if we need to know about the hand-shaking lemma?

doubt it, It has never been asked as far as I am aware.

Hi Gibbo,

I have a couple of questions regarding D1 if you could please give me some tips :

1) In Djikstra's algorithm, sometimes they actually add a value in and sometimes they just add the smallest value in the mark scheme...

for instance, if there are two paths to B, one of length 57 and one of length 46..sometimes they'll put 57 46 and sometimes it will be just 46. When do you know when to put each one in?

2) Any tips on drawing a network from a precedence table? I find it difficult.

3) How likely is scheduling to come up? Arsey said it hasn't come up since January 2007 and therefore is unlikely to come up, however I'd argue the opposite : If it hasn't come up since 07' then there may be a higher chance of it coming up!

Thanks

The hand shaking lemma is about why there are only even numbers of odd vertices.

It has been asked in the past but never called the hand shaking lemma.

The reason is that the total order (or valency) of any network is even so there must be an even number of odd nodes. The reason for this is that every edge contributes two to the overall order so the total order must be number of edges x 2 so even.

Hi everyone,
I really need help with how to tackle scheduling. I've had to self-teach myself D1 as none of the teachers at my school can teach it.
I'm really stressing as I can't seem to get scheduling questions right. I've looked through the textbook and it doesn't seem to give much help. Also, I've tried searching online for notes, but there don't seem to be any for scheduling.
If anyone could help me, it would be greatly appreciated - I get really stressy before exams and this isn't helping!
any help would be much appreciated

??

Basically scheduling is tricky because there is no hard and fast way that I can tell you to do it that will guarentee that you'll get it right. I can however give you some tips:

1. Keep your diagram neat. Use about 1cm for each row and 1 row per worker.

2. Start with the critical path. Assign this to worker 1. This should fill his row.

3. If there are any other critical activities assign them to the next row. Since they're critical there is no choice of where to put them.

4. Now right down a list in alphabetical order of the remaining activities. As you add them to the diagram cross them out. This will reduce the chance of you missing one out.

5. Fill in the remaining rows with the remaining activities. Try as much as you can to have them starting at their 'early event time'.

6. If you have to have any starting later (using their float) remember that this will have a knock on effect to any dependent activities.

7. When ever you cant fit an activity in use a new line/worker.

8. Take your time and don't panic