Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Next number in the pattern?

  1. Aug 1, 2006 #1
    I took this stupid quiz on finding the next number in the pattern, and at the end, it didn't tell me the right answers!!!

    the one that stumped me was: 73, 61, 56. 62, ?

    anyone know the answer?
  2. jcsd
  3. Aug 2, 2006 #2
    My only guess after skimming at it would be 39...that would fit in the pattern so far...but I don't know if it's right. Every other number subtracts 17, while the other opposite set would add 1 each time....but that's probably wrong.
  4. Aug 2, 2006 #3


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    I think the goal is to find the general term [itex]a_n[/itex] of the sequence.
  5. Aug 2, 2006 #4
    well just giving you 4 terms doesn't tell you anything about the general form. 39 is as good an answer as any. Obviously you can make the rest of the terms whatever you want. What sort of quiz was this? Silly questions :smile:

    As for whether it's part of a well-known sequence of interest, the online integer sequence encyclopedia gives no results.
  6. Aug 2, 2006 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    First it decreases by 12, then 5, then increases by 1. So the change in the increase/decrease goes:
    6, 5. My guess is the increase would increase by 4, meaning the next term would be 5 greater, or 67

    But there's no obvious pattern involved, because the second and third term are part of a decreasing sequence, but the fourth term is greater than the third
  7. Aug 2, 2006 #6


    User Avatar
    Homework Helper

    I agree, it doesn't seem like there is enough information. You could always fit a polynomial to the points (1,73),( 2,61), etc, and extend the series that way (which is essentially what you're doing when you look at the difference between the difference between ... between the difference of consecutive terms (see the method of differences used in Babbages' http://en.wikipedia.org/wiki/Difference_engine" [Broken]) ). What is the context of the problem? Give some more examples from this problem set. Should we look at mathematical properties like the prime factorizations or sums of digits, or could it be something like the number of days in certain months of the year?
    Last edited by a moderator: May 2, 2017
  8. May 27, 2011 #7
  9. May 28, 2011 #8
    My guess is 0, since it is the only other root of the polynomial


    But seriously, this is silly. Only giving 4 terms is not enough to deduce a pattern. But I think the guess of Vatican Hell is the best you can make...
  10. May 29, 2011 #9
    You're exaggerating! ;)
    It wasn't so hard
    73: (7-3) x3 ...
  11. May 30, 2011 #10
    Gotta agree with Manu Mop here. Given integer ab, where a,b are part of the counting integers 0 to 9, the next number is ab-((a-b)*b)


    Bit obscure, but it fits...
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook