Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.

Trending News

Promoted
?
? asked in Science & MathematicsMathematics · 8 years ago

How much is 1+2+3+4+5+6+7+8+9+8+7+6+5+4+3+2+1?

just curious...:)

7 Answers

Relevance
  • Demiurge42
    Lv 7
    8 years ago
    Favorite Answer

    1+2+3+4+5+6+7+8+9+8+7+6+5+4+3+2+1 =

    1+2+3+4+5+6+7+8+9+

    8+7+6+5+4+3+2+1

    ____________________

    9+9+9+9+9+9+9+9+9 =

    9*9 = 81

  • MICHAEL K
    Lv 7
    8 years ago

    81

  • ILoveViolet
    8 years ago

    81

  • 037 G
    Lv 6
    8 years ago

    81

  • How do you think about the answers? You can sign in to vote the answer.
  • ?
    8 years ago

    81

    Source(s): My head
  • Adarsha Pokhrel
    8 years ago

    using the formula for sum of n number of integers from 1 to n n(n + 1)/2

    we get

    the sum from 1 to 9 = 45

    sum from 1 to 8 = 36

    so net sum is = 36+45 = 81

    Source(s): aa
  • Big Orange
    Lv 6
    8 years ago

    punch it in a calculator...81

Still have questions? Get your answers by asking now.