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  1. 1 + 3 + 5 + 7 + 9 + ... + 97 + 99 Look at the first and last numbers : 1 + 99 Then the next two: 3 + 97 Then the next two 5 + 95 etc. 49 + 51 They all add up to 100 and you have 25 pairs. Answer: 2500 Another way ...

    11 Answers · Science & Mathematics · 05/09/2008

  2. The sum of the squares of the odd numbers from 1 to 99 ( 100 isn't included as it is even...i= 1 to 49) i^2 + 4 * sum(i= 1 to 49) i + sum(i= 1 to 49) 1 = 1 + 4 * 49(49 + 1 )(98 + 1 )/6 + 4 * 49(49...

    3 Answers · Science & Mathematics · 15/08/2010

  3. From 1 to 100 you have 100 numbers . The average ...50-20 = 30 but since both end numbers are counted you add 1 . 30+ 1 =31. To see this count the number...

    8 Answers · Science & Mathematics · 29/10/2007

  4. ...the sum is the product of n and the even number between the two middle numbers . For 1 - 100 , this works out to be 50. And for 1 - 1000, it does work out to be 418 (http://en.wikipedia...

    2 Answers · Science & Mathematics · 04/12/2009

  5. The sum of the squares of the even numbers from 1 to 100 is: 2^2 + 4^2 + 6^2 + ... + 100 ^2 => sum(i= 1 to 50) (2i)^2 = sum(i= 1 ...

    2 Answers · Science & Mathematics · 15/08/2010

  6. ...101 2 + 99 = 101 3 + 98 = 101 ... 49 + 52 = 101 50 + 51 = 101 The sum of all numbers from 1 to 100 , should be the same as adding 101 to itself 50 times By...

    8 Answers · Science & Mathematics · 27/12/2017

  7. You pair them off: 1 +99 = 100 2 + 98 = 100 3 + 97 = 100 ... 48+52 = 100 49 + 51 = 100 That's 49...http://en.wikipedia.org/wiki/Arithmetic_series#Sum_.28arithmetic_series.29 1 + 2 + ... + n = n(n+ 1 ) / 2

    7 Answers · Science & Mathematics · 01/08/2007

  8. ...give it a try. First, write out all the numbers from 1 to 100 . It will be convenient if you lay... is complete for the numbers 1 to 100 . Every number that is...

    4 Answers · Science & Mathematics · 03/07/2009

  9. ...in his head in under 10 seconds. He reasoned thus: 1 + 100 = 101 2 + 99 = 101 3 + 98 = 101 There are fifty such pairs, each adding up to 101. 50 x 101 = 5,050.

    14 Answers · Science & Mathematics · 16/07/2007

  10. ...then there are 100 *101/2 = 5050 dots which is also the sum from 1 to 100 .

    5 Answers · Science & Mathematics · 31/07/2011

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