Q. Find the value of the following expression and round to the nearest integer:n=2∑20700(0.71)n−1Answer:
Given series parameters: We are given a geometric series with the first term a=700(0.71)2−1=700(0.71) and the common ratio r=0.71. The sum of a finite geometric series is given by the formula Sn=(1−r)a(1−rn), where n is the number of terms. First, we need to find the number of terms in the series.
Calculate number of terms: The series starts at n=2 and ends at n=20, so the number of terms is 20−2+1=19. Now we can use the formula for the sum of a geometric series to find the sum.
Calculate sum formula: Plugging the values into the formula, we get S19=700(0.71)(1−0.7119)/(1−0.71). Let's calculate the sum.
Calculate common ratio: First, calculate 0.7119 using a calculator to ensure accuracy. 0.7119≈0.0059 (rounded to four decimal places for simplicity).
Substitute values into formula: Now, substitute this value into the sum formula: S19≈700(0.71)(1−0.0059)/(1−0.71).
Calculate numerator subtraction: Perform the subtraction in the numerator: 1−0.0059=0.9941.
Calculate denominator subtraction: Now, perform the subtraction in the denominator: 1−0.71=0.29.
Calculate numerator multiplication: Multiply the numerator: 700×0.71×0.9941≈494.287.
Calculate division: Divide by the denominator: 494.287/0.29≈1704.438.
Round final result: Round the result to the nearest integer: 1704.438 rounds to 1704.
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