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Find the sum of the first 8 terms of the following series, to the nearest integer.

3,(15)/(4),(75)/(16),dots
Answer:

Find the sum of the first 88 terms of the following series, to the nearest integer.\newline3,154,7516, 3, \frac{15}{4}, \frac{75}{16}, \ldots \newlineAnswer:

Full solution

Q. Find the sum of the first 88 terms of the following series, to the nearest integer.\newline3,154,7516, 3, \frac{15}{4}, \frac{75}{16}, \ldots \newlineAnswer:
  1. Identify Pattern: Identify the pattern of the series.\newlineThe series is geometric because each term is multiplied by a common ratio to get the next term. To find the common ratio (r), divide the second term by the first term.\newliner=15/43=15413=1512=54 r = \frac{15/4}{3} = \frac{15}{4} \cdot \frac{1}{3} = \frac{15}{12} = \frac{5}{4}
  2. Use Formula: Use the formula for the sum of the first n terms of a geometric series, which is Sn=a1(1rn)1r S_n = \frac{a_1(1 - r^n)}{1 - r} , where a1 a_1 is the first term, r r is the common ratio, and n n is the number of terms.\newlineHere, a1=3 a_1 = 3 , r=54 r = \frac{5}{4} , and n=8 n = 8 .
  3. Calculate Sum: Calculate the sum of the first 88 terms using the formula.\newlineS8=3(1(54)8)154 S_8 = \frac{3(1 - (\frac{5}{4})^8)}{1 - \frac{5}{4}}
  4. Simplify Denominator: Simplify the denominator of the fraction.\newline154=4454=14 1 - \frac{5}{4} = \frac{4}{4} - \frac{5}{4} = -\frac{1}{4}
  5. Calculate Exponent: Calculate (54)8 (\frac{5}{4})^8 to find the numerator.\newline(54)8 (\frac{5}{4})^8 is a large number, so it's best to use a calculator for this step.
  6. Substitute and Calculate: Substitute the values into the sum formula and calculate.\newlineS8=3(1(54)8)14 S_8 = \frac{3(1 - (\frac{5}{4})^8)}{-\frac{1}{4}} \newlineUsing a calculator, (54)81525.87890625 (\frac{5}{4})^8 \approx 1525.87890625 \newlineS8=3(11525.87890625)14 S_8 = \frac{3(1 - 1525.87890625)}{-\frac{1}{4}}
  7. Simplify Numerator: Simplify the numerator.\newline11525.878906251524.87890625 1 - 1525.87890625 \approx -1524.87890625 \newlineS8=3(1524.87890625)14 S_8 = \frac{3(-1524.87890625)}{-\frac{1}{4}}
  8. Multiply and Divide: Multiply the numerator by 33 and divide by the denominator.\newlineS8=4574.6367187514 S_8 = \frac{-4574.63671875}{-\frac{1}{4}} \newlineS8=4574.63671875(4) S_8 = -4574.63671875 \cdot (-4) \newlineS8=1830.6546875 S_8 = 1830.6546875
  9. Round to Nearest: Round the sum to the nearest integer.\newlineS81831 S_8 \approx 1831

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