SOLUTION: A partial sum of the arithmetic series is given. Find the sum: 3 + 5 + 7 + . . . + 101.

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Question 849384: A partial sum of the arithmetic series is given. Find the sum: 3 + 5 + 7 + . . . + 101.
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

d = 2

 a%5Bn%5D=a%5B1%5D%2B%28n-1%29%2Ad    Finding which 'n'  for 101 

  a%5Bn%5D=+3%2B%28n-1%29%2A2+=+101

          2n + 1 = 101,  n = 50

S%5Bn%5D=%28n%28a%5B1%5D%2Ba%5Bn%5D%29%29%2F2

S%5B50%5D=%2850%283%2B101%29%29%2F2= 2600

Following may also be used

S%5Bn%5D=%28n%2F2%29%282%2Aa%5B1%5D%2B+%28n-1%29d%29