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Find the value of the following expression and round to the nearest integer:

sum_(n=2)^(20)700(0.71)^(n-1)
Answer:

Find the value of the following expression and round to the nearest integer:\newlinen=220700(0.71)n1 \sum_{n=2}^{20} 700(0.71)^{n-1} \newlineAnswer:

Full solution

Q. Find the value of the following expression and round to the nearest integer:\newlinen=220700(0.71)n1 \sum_{n=2}^{20} 700(0.71)^{n-1} \newlineAnswer:
  1. Given series parameters: We are given a geometric series with the first term a=700(0.71)21=700(0.71)a = 700(0.71)^{2-1} = 700(0.71) and the common ratio r=0.71r = 0.71. The sum of a finite geometric series is given by the formula Sn=a(1rn)(1r)S_n = \frac{a(1 - r^n)}{(1 - r)}, where nn is the number of terms. First, we need to find the number of terms in the series.
  2. Calculate number of terms: The series starts at n=2n=2 and ends at n=20n=20, so the number of terms is 202+1=1920 - 2 + 1 = 19. Now we can use the formula for the sum of a geometric series to find the sum.
  3. Calculate sum formula: Plugging the values into the formula, we get S19=700(0.71)(10.7119)/(10.71)S_{19} = 700(0.71)(1 - 0.71^{19}) / (1 - 0.71). Let's calculate the sum.
  4. Calculate common ratio: First, calculate 0.71190.71^{19} using a calculator to ensure accuracy. 0.71190.00590.71^{19} \approx 0.0059 (rounded to four decimal places for simplicity).
  5. Substitute values into formula: Now, substitute this value into the sum formula: S19700(0.71)(10.0059)/(10.71)S_{19} \approx 700(0.71)(1 - 0.0059) / (1 - 0.71).
  6. Calculate numerator subtraction: Perform the subtraction in the numerator: 10.0059=0.99411 - 0.0059 = 0.9941.
  7. Calculate denominator subtraction: Now, perform the subtraction in the denominator: 10.71=0.291 - 0.71 = 0.29.
  8. Calculate numerator multiplication: Multiply the numerator: 700×0.71×0.9941494.287700 \times 0.71 \times 0.9941 \approx 494.287.
  9. Calculate division: Divide by the denominator: 494.287/0.291704.438494.287 / 0.29 \approx 1704.438.
  10. Round final result: Round the result to the nearest integer: 1704.4381704.438 rounds to 17041704.

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