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  1. J

    Normal distribution - Finding mean and standard deviation

    Many thanks for the reply, and you are correct. I was using the table wrong and now understand how it all works properly. Thanks for taking the time to reply. JAmes
  2. J

    Normal distribution - Finding mean and standard deviation

    Thanks for the reply, but I get that part. I was wondering about the values of 0.8779 and -0.5534 I think they are correct for the corresponding probabilities but the answer got different values. So it's actually the Z1 and Z2 values I need checking. After that, I'm fine. CHeers James
  3. J

    Normal distribution - Finding mean and standard deviation

    Homework Statement A high jumper knows from experience that she can clear a height of at least 1.78m once in 5 attempts. She also knows that she can clear a height of at least 1.65m on 7 out of 10 attempts. Find to 3 dp the mean and standard deviation of the heights the jumper can reach...
  4. J

    Geometric Distribution Question

    Cheers! I know the actualy calculation is done right. Just wasn't completly sure if I'd used the right method. I stupidly left the notes I did for the question at University and I'm revising now at home so can't check over them.
  5. J

    Geometric Distribution Question

    Homework Statement An experiment consistion of tossing three fair coins is performed repeatedly and "success" is when all three show a head. What is the probability that the success is on the third performance of the experiment? Homework Equations Geometric distribution equation p(x) =...
  6. J

    Velocity of a proton question

    So would the correct answer be... 120 * 1.6 x 10-19 = 1.92 x 10 -17 sqrt(2*1.92 x 10 -17/1.7 x 10-27) = v = 1.5 x 105 ms-1
  7. J

    Velocity of a proton question

    By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electrostatic potential difference of one volt. (from Wiki) Oh, my tutor told me to divide... Is it because 1 Volt = 1 Joule/1 Coulomb There for Joules = V * C...
  8. J

    Differential Equation Uses

    We did the basics of solving differential equations in Maths this week, well, it was actually just finding other approximate values of y for an equation given the derivative and a pair of co-ordinates on it. Are these for equations that cannot be subject to intergration? Also, what can...
  9. J

    Velocity of a proton question

    Homework Statement Calculate the veolcity of a proton of energy 0.12 keV proton mass = 1.7 x 10^-27 Homework Equations The Attempt at a Solution I thought... 0.12 keV = 120 eV 120/1.60 x 10^-19 = 7.5 x 10^20 J E = 0.5mv^2 sqrt(2E/m) = v but I'm getting something to x 10^23 so its...
  10. J

    Roots of a cubic equation

    Many many thanks for your replies, I think I will try and have a go at studying the things you mentioned in your first post for definate! Anything that will expand my knowledge and help me at University can only be a good thing! I managed to get the answer by creating a linear and quadratic...
  11. J

    Roots of a cubic equation

    I've been looking at some practise exams for the University I would like to apply to, I have to sit the exam on 4th November. We have never done finding the roots of a cubic equation before and I cannot figure it out from looking on the internet, the formulas are all horrible to understand...
  12. J

    Derivative of a sum of functions, also cubic graph roots

    Thanks alot for that, didn't realise that was it, glad they are something easy & not hard. I will do a bit of digging on the cubic then and try to work it out ;)
  13. J

    Derivative of a sum of functions, also cubic graph roots

    Derivative of a sum of functions What would you interperate this as? It is one of the subsections of Differentiation from the syllabus of a University entrance Exam in November but I cannot think what it is refering to. Differentiation: Derivative of xa, including for fractional...
  14. J

    RSA Algorithm Help

    I think you are right but I am getting fractions when the modulus function is introduced as I'm unsure how it works. James
  15. J

    RSA Algorithm Help

    Can anyone help with this? Will ask my math/physics teacher tomorrow but wouldnt mind having another go at it first. Cheers James
  16. J

    RSA Algorithm Help

    I'm not sure. Thats where I think I have gone wrong though. Think I messed up at kj = 1 (mod z) 7j = 1 (mod 8) trying to work out the private key as I have tried to teach myself how to do this from an example on a website without really knowing how to do it. James
  17. J

    RSA Algorithm Help

    Struggling to put a number through this as I keep getting my original number as the encrypted number too. A = 11 p = 3 q = 5 n = pq = 15 z = (p-1)(q-1) = 2*4 = 8 k = co-prime of z = 7 So, A=11 n=15 z=8 (Public key) k=7(Public key) kj = 1 (mod z) 7j = 1 (mod 8) for which I am getting j =...
  18. J

    Maths Behind Credit Card Transactions

    I'm having a go at the RSA at the moment, just sticking some values through it to see if I can get it to work. I will try & check out Schneier's books too. Just wondering if anyone knows, when you first introduce (mod x) into it, does the remainder (R) have to be a set amount? eg, I have 13*j...
  19. J

    Maths Behind Credit Card Transactions

    Not that I know of, never heard it mentioned anyway. This is what I am doing... http://www.ocr.org.uk/Data/publications/key_documents/L_GCE_Maths_Spec.pdf [Broken] On page 4, I have done 5.1, 5.2 & 5.16 Currently studying - 5.3 And going on to do 5.4, 5.5, 5.6, 5.7 & 5.8 next year if it...
  20. J

    Maths Behind Credit Card Transactions

    I will have a quick scan over the elliptical curves, do you know anywhere online where I can read up on some of the number theory theorems as I have ne knowlage of it as of yet. Cheers james
  21. J

    Maths Behind Credit Card Transactions

    Thank you for the reply, just looked at those authors, quite expensive books so will ask my local libery to get some copies, or request anyway! Just looked up RSA & I presume you mean the algorithm. Looks fairly complicated but I try going over it tonight & see if I can make sense of what is...
  22. J

    Maths Behind Credit Card Transactions

    I am doing a qualification which requires me to chooses a subject for which I will research & produce a presentation & a 5000 word essay in December. As I plan to study maths at Degree Level I have decided to do a maths based project. My two basic ideas are.... How does Maths keep our...
  23. J

    Force on a surface

    That will probably be what we would be measuring then I assume. My idea was based on an experiment that we are going to be doing soon. We were going to try & make a listening device to detect vibrations on objects. put something reflective on a low frequency speaker & fire a laser onto it...
  24. J

    Force on a surface

    I was talking to my physics teacher the other day & he was saying about measuring the force exerted by an object on a surface if it is dropped onto it. The example we were using was dropping ball bearings onto a table (we are currently studying momentum) If I have got the above correct, what...
  25. J

    Shock absorber/Suspension advice (bike project)

    After reading an article a few weeks ago about a man who had made a bicycle with a triangular & pentagonal wheel & started doing some reading on the shapes. Made a model of it but would like to try & make a full size one as we realised that it needs some parts that I couldnt make out of...
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