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Homework Help: Addition of big numbers

  1. Nov 1, 2016 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
    hey hello every one I want to ask a question that is add 1+2+3+4..............10000000. I think its very easy. for example let us add first 5 numbers 1+2+3+4+5 now we can find a pattern that adding first and last digit will be always same. for example 5+1=4+2 and similarly but it is a odd number that we can Ind easily by simple maths. so here we can multiply 6(addition of first and last number)×2(number of pairs) +3 because it is odd number
  2. jcsd
  3. Nov 1, 2016 #2

    I know I should write question separately but I couldn't
  4. Nov 1, 2016 #3


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    Gold Member

    So what is your question? Is it simply "how do you add 1 + 2 + 3 + ... + n" ? If so, you need to show some attempt to do this yourself. HINT: it is trivially easy.
  5. Nov 1, 2016 #4


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    Staff: Mentor

    The pairing of the greatest with the smallest number and working inwards looks fine.
    Can you derive a formula for it, say 1+2+...+n for even n?
    And for odd n, what happens if you apply your formula then on n-1 and add n separately?
  6. Nov 1, 2016 #5


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    Gold Member

    Yes. For ANY n. Try it. We don't spoon feed answers here, you have to show some work.
  7. Nov 1, 2016 #6
    You may try to guess the formula by visualising the pattern. For example, draw one dot in the first line, two dots in the second, so on and so forth. Can you observe any pattern of the total number of dots?
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