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Find the sum of the first 38 terms of the following series, to the nearest integer.

3,9,15,dots
Answer:

Find the sum of the first 3838 terms of the following series, to the nearest integer.\newline3,9,15, 3,9,15, \ldots \newlineAnswer:

Full solution

Q. Find the sum of the first 3838 terms of the following series, to the nearest integer.\newline3,9,15, 3,9,15, \ldots \newlineAnswer:
  1. Identify type and difference: Identify the type of series and the common difference.\newlineThe given series is arithmetic because there is a constant difference between consecutive terms.\newlineTo find the common difference dd, subtract the first term from the second term.\newlined=93=6d = 9 - 3 = 6
  2. Use arithmetic series formula: Use the formula for the sum of an arithmetic series.\newlineThe sum of the first nn terms of an arithmetic series can be found using the formula:\newlineSn=n2×(2a+(n1)d)S_n = \frac{n}{2} \times (2a + (n - 1)d)\newlinewhere SnS_n is the sum of the first nn terms, aa is the first term, and dd is the common difference.
  3. Plug in values: Plug in the values into the formula to find the sum of the first 3838 terms.\newlineLet's use the formula with n=38n = 38, a=3a = 3, and d=6d = 6.\newlineS38=382×(2×3+(381)×6)S_{38} = \frac{38}{2} \times (2 \times 3 + (38 - 1) \times 6)
  4. Simplify expression: Simplify the expression to find the sum.\newlineS38=19×(6+37×6)S_{38} = 19 \times (6 + 37\times6)\newlineS38=19×(6+222)S_{38} = 19 \times (6 + 222)\newlineS38=19×228S_{38} = 19 \times 228\newlineS38=4332S_{38} = 4332

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