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Find the sum of the first 25 terms in this geometric series:

8+6+4.5 dots
Choose 1 answer:
(A) 0.03
(B) 4.57
(C) 29.91
(D) 31.98

Find the sum of the first 2525 terms in this geometric series:\newline8+6+4.5 8+6+4.5 \ldots \newlineChoose 11 answer:\newline(A) 00.0303\newline(B) 44.5757\newline(C) 2929.9191\newline(D) 3131.9898

Full solution

Q. Find the sum of the first 2525 terms in this geometric series:\newline8+6+4.5 8+6+4.5 \ldots \newlineChoose 11 answer:\newline(A) 00.0303\newline(B) 44.5757\newline(C) 2929.9191\newline(D) 3131.9898
  1. Identify Terms and Ratio: Identify the first term a1a_1, common ratio rr, and number of terms nn in the geometric series.\newlineThe first term a1a_1 is 88, the second term is 66, and the third term is 4.54.5. To find the common ratio rr, we divide the second term by the first term.\newliner=68=0.75r = \frac{6}{8} = 0.75\newlineThe number of terms nn is given as rr00.
  2. Use Sum Formula: Use the formula for the sum of the first nn terms of a geometric series: Sn=a1×(1rn)/(1r)S_n = a_1 \times (1 - r^n) / (1 - r), where SnS_n is the sum of the first nn terms, a1a_1 is the first term, rr is the common ratio, and nn is the number of terms.\newlinePlug in the values we have: a1=8a_1 = 8, r=0.75r = 0.75, and n=25n = 25.\newlineSn=a1×(1rn)/(1r)S_n = a_1 \times (1 - r^n) / (1 - r)00
  3. Calculate Sum: Calculate the sum using the values from the previous step.\newlineS25=8×(10.7525)/(10.75)S_{25} = 8 \times (1 - 0.75^{25}) / (1 - 0.75)\newlineS25=8×(10.7525)/0.25S_{25} = 8 \times (1 - 0.75^{25}) / 0.25\newlineSince 0.75250.75^{25} is a very small number, we can approximate it to 00 for the sake of simplicity in calculation.\newlineS258×(10)/0.25S_{25} \approx 8 \times (1 - 0) / 0.25\newlineS258/0.25S_{25} \approx 8 / 0.25\newlineS2532S_{25} \approx 32
  4. Check Answer Choices: Check the answer choices to see which one matches our calculated sum. The closest answer to our calculated sum of 3232 is (D) 31.9831.98.

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