You are Here: Home >< Maths

# OCR D1 Mon 25th watch

1. (Original post by MikeyBee)
What the hell did that packing question even test! So so annoying, with literally 5 more minutes I could have gained at least another 5 marks. On the whole wasn't too hard, especially considering my 20 minutes of revision - only problem was time limit. And that ridic 1/2n (n-1) guy that made no sense.

I too like some others got x=4 y=6 z=2 for the gym one!

Question on the simplex tableau, when given the 'Maximise' bit (i.e. P=) did you have to inverse the whole equation when putting it in the table (e.g. Maximise 2x plus 3y - 4z goes to -2x - 3y plus 4z) cos this could have cost me like 11 marks.
yes sorry you had to inverse it
2. hi! i just did the ocr d1 paper yesterday nd hv officially failed it! it ws d hardest and most confusing one i hd evr seen
I ws wondering if people cud tell me how they found it? do dey feel d same as me or r dey quite happy wid d paper??
3. Your spelling probably won't help either..
4. (Original post by Little Miss ALevels)
yes sorry you had to inverse it
i was wondering how you guys know that for the simplex ques, the objective had to be inversed??
I thought they had guided us through the whole thing within the different steps already
5. (Original post by khalaf)
Your spelling probably won't help either..
haha! true......but i luckily didn't use any slang language with my D1 paper
6. (Original post by shreedipta)
haha! true......but i luckily didn't use any slang language with da D1 paper
I'm sure you didn't..
7. Has anyone worked out how to do question 6(i) and 6 (ii) from this OCR D1 exam? Here's what it said -
(i) If Dominic uses a network with 5 vertices, what is the greatest number of arcs that he needs? What is greatest number of arcs that he needs for a network with n vertices?
(ii)(a) If he uses a shuttle sort to order the weights of the arcs, with 5 vertices, what is the maximum number of passes, the max number of comparisons in the 1st, 2nd and 3rd passes and what is the maximum number of comparisons overall.
(ii) (b) Show that the max number of comparisons for a network with n vertices is
1/4*n(n-1)(1/2*n(n-1)-1).
I get the answers to these to be:
(i)10, n(n-1)/2
(ii) (a) max passes = 4, max comps = 1,2,3, total comps = 15
But I can't get the last part. Any help? Anyone know what to do?
8. Okay so for the last part there are n vertices therefore 0.5n(n+1) arcs. which need to be sorted. Remember for 5 arcs you'll need 4 passes for for 0.5n(n-1) you'll need 0.5n(n-1) - 1 passes (one fewer than the total). For 4 passes you use 1 + 2 + 3 + 4 comparisons. This is the same as the formula given at the start of the paper so for 0.5n(n-1) - 1 passes you'll need a total of 0.5[0.5n(n-1) - 1][0.5n(n-1) - 1 + 1)]. This simplifies to 0.5[0.5n(n-1) -1][0.5n(n-1)] which is what they ask you to prove. The trick to this is combining parts (i) and (ii)(a) to get (ii)(b). NASTY QUESTION !

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: May 6, 2010
Today on TSR

Will it ever be possible?

### University open days

1. University of Cambridge
Wed, 26 Sep '18
2. Norwich University of the Arts
Fri, 28 Sep '18
3. Edge Hill University
Faculty of Health and Social Care Undergraduate
Sat, 29 Sep '18
Poll
Useful resources

Can you help? Study help unanswered threadsStudy Help rules and posting guidelinesLaTex guide for writing equations on TSR

## Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE