Averages

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by mba1986 » Mon Aug 23, 2010 9:16 pm
1. The sum of the even numbers between 1 and n is 79*80, where n is an odd number, then n=?

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by kvcpk » Mon Aug 23, 2010 11:12 pm
arjunsekhar wrote:1. The sum of the even numbers between 1 and n is 79*80, where n is an odd number, then n=?
2,4,6,....2k is the series of items where n=2k+1

2(1+2+3+...k)
=2(k(k+1))/2
=k(k+1) = 79*80
Hence k should be 79

Hence n= 2(79) +1 = 159

Hope this helps!!
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