SOLUTION: What is the correct way to find the sum of 1+4+7+10+13......100

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Question 11037: What is the correct way to find the sum of 1+4+7+10+13......100
Answer by longjonsilver(2297) About Me  (Show Source):
You can put this solution on YOUR website!
one formula is S%5Bn%5D+=+n%2F2%28a%2Bl%29 where a is first term and l is last term.

Issue is, how many terms?, well 3,6,9,...,102 is the 3-times table with 34 terms.

1,4,7,...,100 is the same set of numbers, shunted down by 2... so 34 terms.

so, S%5B34%5D+=+34%2F2%281%2B100%29
S%5B34%5D+=+17%28101%29
S%5B34%5D+=+1717

jon.