SOLUTION: Find the sum of the first 30 terms of an arithmetic series if the 1st term is 5 and the 30th term is 100.

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Question 1206543: Find the sum of the first 30 terms of an arithmetic series if the 1st term is 5 and the 30th term is 100.
Answer by ikleyn(52775) About Me  (Show Source):
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Find the sum of the first 30 terms of an arithmetic series if the 1st term is 5 and the 30th term is 100.
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Use the formula for the sum of the first n terms of an AP in the form

    S%5Bn%5D = %28%28a%5B1%5D%2Ba%5Bn%5D%29%2F2%29%2An = %28%285%2B100%29%2F2%29%2A30 = (5+100)*15 = 105*15 = 1575.    ANSWER

Solved.

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For introductory lessons on arithmetic progressions see
    - Arithmetic progressions
    - The proofs of the formulas for arithmetic progressions
    - Problems on arithmetic progressions
    - Word problems on arithmetic progressions
in this site.