SOLUTION: Use summation notation to write the arithmetic series for the specified number of terms. Then find the sum. 6 + 7.4 + 8.8 +...; n=11 I don't understand. Please help!

Question 1001269: Use summation notation to write the arithmetic series for the specified number of terms. Then find the sum.
6 + 7.4 + 8.8 +...; n=11
I don't understand. Please help!
Found 2 solutions by fractalier, solver91311:
Answer by fractalier(6550) (Show Source): You can put this solution on YOUR website!
You would write n = 1 under the sigma.
You would write n = 11 over the sigma.
Since the terms go up by 1.4, the general term would be
a(n) = 6 + 1.4(n-1) = 1.4n + 4.6
You put this after the sigma.
To find the sum, add the first and last terms and multiply that sum by half the number of terms, or
Sum = (n/2)(a(1)+a(n))
Sum = (11/2)(6 + 20) = 143
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!

or

The two expressions are equivalent. To get the sum, you can either write out all of the 11 terms and add them, or use the formula for the sum of an arithmetic series: (First Number + Last Number) times the number of numbers divided by 2.

John

My calculator said it, I believe it, that settles it

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