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

How do you find the sum of the digits of number N? Say N = 10

  1. Jan 12, 2004 #1
    How do you find the sum of the digits of number N?


    Say N = 10
     
  2. jcsd
  3. Jan 12, 2004 #2
    If memory serves me correctly:

    [tex]
    \sum_{k=1}^N k= \frac{N(N+1)}2
    [/tex]

    a fact that you would prove by induction.
     
  4. Jan 13, 2004 #3

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Was that what was meant? The "sum of the digits" of 10 is 1+ 0= 1, of course.
     
  5. Jan 13, 2004 #4
    It will be true only if the digits form a Arithmetic Projection
    for eg N=2468 etc {2+4+6+8}
    but not in general say for N=12245 {1+2+2+4+5}
     
  6. Jan 13, 2004 #5
    You're right, I answered a completely different question. Well, I am sure someone asked my question somewhere, sometime. :)
     
  7. Jan 13, 2004 #6

    Yea what if N = 1231247839783924723840723084732084738274... + ... N?
     
  8. Jan 14, 2004 #7
    Ofcourse it would be
    as N=1+0
    here it will be N=1+2+3+1+2+4+7+8+3+9+7+8+3+9+2+4+7+2+3+8+4+0+7+2+3+0+8+4+7+3+2+0+8+4+7+3+8+2+7+4+...+x+y+z+a+b+c+d :wink: :wink: :wink:
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: How do you find the sum of the digits of number N? Say N = 10
  1. Find the sum S(n) (Replies: 10)

Loading...