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31 December, 02:31

What is the sum of the first 19 terms of an arithmetic series with a rate of increase of 7 and a7 = 46?

A. 1,197

B. 1,273

C. 1,373

D. 1,423

E. 1,327

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Answers (1)
  1. 31 December, 06:02
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    Calculate for the first term of the series

    an = (a1) x (n - 1) x d

    Using the value of a7 = 46 and the rate of increase

    46 = (a1) x (7 - 1) x 7

    The value of a1 is 4.

    Solving for the sum of 19 terms,

    Sn = (n/2) x (2a1 + (n - 1) x d)

    Substituting,

    Sn = (19/2) x ((2) (4) + 18 x 7)

    The sum of the first 19 terms is 1,273. Therefore, the answer is letter B.
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