Q. Find the value of the following expression and round to the nearest integer:n=2∑5720(1.15)n−2Answer:
Given geometric series: We are given a geometric series with the first term a=20(1.15)2−2=20 and a common ratio r=1.15. The sum of a finite geometric series can be found using the formula Sn=1−ra(1−rn), where n is the number of terms.
Determine number of terms: First, we need to determine the number of terms in the series. Since the series starts at n=2 and goes to n=57, the number of terms is 57−2+1=56.
Apply sum formula: Now we can apply the formula for the sum of a geometric series: Sn=a(1−rn)/(1−r). Plugging in the values, we get S56=20(1−1.1556)/(1−1.15).
Calculate numerator: Let's calculate the numerator of the fraction: 1−1.1556. Using a calculator, we find that 1.1556≈142.061.
Calculate denominator: Subtracting this from 1 gives us 1−142.061≈−141.061.
Divide numerator by denominator: Now we calculate the denominator of the fraction: 1−1.15=−0.15.
Multiply by first term: We can now divide the numerator by the denominator: −141.061/−0.15≈940.407.
Round to nearest integer: Multiplying this result by the first term of the series 20 gives us the sum of the series: 940.407×20≈18808.14.
Round to nearest integer: Multiplying this result by the first term of the series 20 gives us the sum of the series: 940.407×20≈18808.14.Finally, we round the result to the nearest integer: 18808.14 rounds to 18808.
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