OCR C2 HELP! Sigma Notation
Maths and statistics discussion, revision, exam and homework help.
-
- Reputation:
- Thread Starter
- Junior Member
- Posts: 31
OCR C2 HELP! Sigma NotationWhen i get questions with the sigma notation, I can't tell if the question is asking for the sum of an arithmetic or geometric progression. So i muddle up the formulae. Can someone tell me the difference if there is one.
Also for a question that says "Given that the geometric progression converges, find the exact value of r". How do I go about solving this? What does converge mean in terms of progressions. ThanksLast edited by rokknroll3r; 17-05-2012 at 21:31. -
- Reputation:
- Overlord in Training
- Posts: 2,215
Re: OCR C2 HELP! Sigma NotationI remember doing this paper, and from what I remember it's geometric.(Original post by rokknroll3r)
When i get questions with the sigma notation, I can't tell if the question is asking for the sum of an arithmetic or geometric progression. So i muddle up the formulae. Can someone tell me the difference if there is one.
Also for a question that says "Given that the geometric progression converges, find the exact value of r". How do I go about solving this? What does converge mean in terms of progressions. Thanks
Converges means it gets smaller and smaller. So the common difference will have to be between 0 and 1. -
- Reputation:
- New Member
- Location: Yorkshire
- Posts: 18
Re: OCR C2 HELP! Sigma NotationHi
well the best thing to do is to calculate the first few terms, U1, U2, U3....this will give you 'a' and will show you whether there is a common difference 'd' or a common ratio 'r'. Therefore showing you whether it is a GP or an AP
Hope that made sense!
If something converges, it gets closer and closer to a particular value
Last edited by superhan; 17-05-2012 at 21:35. -
- Reputation:
- New Member
- Posts: 2
Re: OCR C2 HELP! Sigma Notationwork out each of the terms that its asking you to work out, probably the first 5 or 4, once you've done that then just add then up(Original post by rokknroll3r)
When i get questions with the sigma notation, I can't tell if the question is asking for the sum of an arithmetic or geometric progression. So i muddle up the formulae. Can someone tell me the difference if there is one.
Also for a question that says "Given that the geometric progression converges, find the exact value of r". How do I go about solving this? What does converge mean in terms of progressions. Thanks
Converges means that the series will never meet 0 -
- Reputation:
- New Member
- Location: Yorkshire
- Posts: 18
Re: OCR C2 HELP! Sigma NotationI don't think that's true..(Original post by djmoo)
Converges means that the series will never meet 0
well the best thing to do is to calculate the first few terms, U1, U2, U3....this will give you 'a' and will show you whether there is a common difference 'd' or a common ratio 'r'. Therefore showing you whether it is a GP or an AP 
