SOLUTION: The sum of the first 25 terms of an arithmetic series with a common difference of 5 is 1300. Find the first term of the series.
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Question 855000: The sum of the first 25 terms of an arithmetic series with a common difference of 5 is 1300. Find the first term of the series. Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! The sum of the first 25 terms of an arithmetic series with a common difference of 5 is 1300. Find the first term of the series.
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1st term: a(1)
25th term: a(1)+24d = a(1) + 24*5 = a(1)+120
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Sum Formula: S(n) = (n/2)(a(1)+last term))
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1300 = (25/2)(a(1)+a(1)+120))
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2600 = 25[2(a(1))+120
104 = 2*a(1) + 120
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2*a(1) = -16
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a(1) = -8
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Cheers,
Stan H.
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