SOLUTION: find the sum of the first 30 terms of 4+7+10+13+16+19....

Question 565548: find the sum of the first 30 terms of 4+7+10+13+16+19....
Answer by htmentor(1343) (Show Source): You can put this solution on YOUR website!
find the sum of the first 30 terms of 4+7+10+13+16+19....
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This is an arithmetic sequence with a_1 = 4, and a common difference of 3.
The formula for the n-th term is:
a_n = a_1 + (n-1)d
a_n = 4 + 3(n-1) = 3n + 1
So the 30th term is a_30 = 3*30 + 1 = 91
The sum of the 1st n terms of an arithmetic sequence is:
S_n = (n/2)(a_1 + a_n)
So S_30 = (30/2)(4+91) = 95*15 = 1425
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