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Find the sum of the first 9 terms of the following sequence. Round to the nearest hundredth if necessary.

75,quad66,quad58.08,dots
Sum of a finite geometric series:

S_(n)=(a_(1)-a_(1)r^(n))/(1-r)
Answer:

Find the sum of the first 99 terms of the following sequence. Round to the nearest hundredth if necessary.\newline75,66,58.08, 75, \quad 66, \quad 58.08, \ldots \newlineSum of a finite geometric series:\newlineSn=a1a1rn1r S_{n}=\frac{a_{1}-a_{1} r^{n}}{1-r} \newlineAnswer:

Full solution

Q. Find the sum of the first 99 terms of the following sequence. Round to the nearest hundredth if necessary.\newline75,66,58.08, 75, \quad 66, \quad 58.08, \ldots \newlineSum of a finite geometric series:\newlineSn=a1a1rn1r S_{n}=\frac{a_{1}-a_{1} r^{n}}{1-r} \newlineAnswer:
  1. Identify terms and ratio: Identify the first term a1a_1 and the common ratio rr of the geometric sequence.\newlineThe first term a1a_1 is the first number in the sequence, which is 7575.\newlineTo find the common ratio rr, we divide the second term by the first term.\newliner=6675=0.88r = \frac{66}{75} = 0.88
  2. Use sum formula: Use the formula for the sum of the first nn terms of a geometric series.\newlineWe have a1=75a_1 = 75, r=0.88r = 0.88, and n=9n = 9. The formula for the sum of the first nn terms (SnS_n) of a geometric series is:\newlineSn=a1a1rn1rS_n = \frac{a_1 - a_1 \cdot r^n}{1 - r}
  3. Substitute and calculate: Substitute the values into the formula and calculate the sum.\newlineS9=7575×0.88910.88S_9 = \frac{75 - 75 \times 0.88^9}{1 - 0.88}\newlineNow we calculate the numerator and the denominator separately.\newlineNumerator: 7575×0.88975 - 75 \times 0.88^9\newlineDenominator: 10.881 - 0.88
  4. Calculate numerator: Calculate the numerator.\newline7575×0.889=7575×(0.23357214690901212)7517.517957.482175 - 75 \times 0.88^9 = 75 - 75 \times (0.23357214690901212) \approx 75 - 17.5179 \approx 57.4821
  5. Calculate denominator: Calculate the denominator.\newline10.88=0.121 - 0.88 = 0.12
  6. Divide to find sum: Divide the numerator by the denominator to find the sum.\newlineS9=57.48210.12479.0175S_9 = \frac{57.4821}{0.12} \approx 479.0175
  7. Round the result: Round the result to the nearest hundredth if necessary. S9479.02S_9 \approx 479.02

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