Algebra

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R.K: Junior | Next Rank: 30 Posts; Posts: 14; Joined: Sun May 27, 2012 2:00 am

by R.K » Sun May 27, 2012 2:26 am

If the sum of first n positive integers is equal to n(n+1)/2, then what is the sum of the first 25 positive integers?

Source: Beat The GMAT — Problem Solving | Sun May 27, 2012 2:26 am

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by Anurag@Gurome » Sun May 27, 2012 2:29 am

R.K wrote:If the sum of first n positive integers is equal to n(n+1)/2, then what is the sum of the first 25 positive integers?

Sum of first n positive integers = n*(n + 1)/2
Sum of first 25 positive integers = 25*(25 + 1)/2 = 25*26/2 = 25*13 = 325

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