SOLUTION: Find the sum of the arithmetic sequence: 56, 58, 60, 62, …, 78

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Question 1137607: Find the sum of the arithmetic sequence: 56, 58, 60, 62, …, 78
Answer by josgarithmetic(39618) About Me  (Show Source):
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General term of sequence, 56%2B%28n-1%29%2A2;

78 is at index 56%2B2%28n-1%29=78
2n-2=78-56
2n=78-56%2B2
n=12

Sequence is 12 terms in length.

SUM:
highlight_green%28%2812%2F2%29%2856%2B78%29%29

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