Q. Find the value of the following expression and round to the nearest integer:n=1∑8620(1.02)nAnswer:
Recognize as geometric series: Recognize the sum as a geometric series.The general form of a geometric series is ∑n=0Narn, where a is the first term, r is the common ratio, and N is the number of terms.In this case, a=20(1.02), r=1.02, and N=86.
Use formula for sum: Use the formula for the sum of a finite geometric series.The sum S of the first N terms of a geometric series is given by S=a(1−rN)/(1−r), provided that |r| < 1.Here, we need to adjust the formula because our series starts at n=1, so we subtract the first term (n=0) from the sum.
Calculate sum using formula: Calculate the sum using the adjusted formula.S=20(1.02)(1−(1.02)86)/(1−1.02)−20(1.02)0Since (1.02)0=1, we subtract 20 from the sum.S=20(1.02)(1−(1.02)86)/(−0.02)−20
Perform calculations: Perform the calculations.S=20(1.02)(1−(1.02)86)/(−0.02)−20S=−20(1.02)(1−(1.02)86)/0.02−20S=−20(1.02)(1−(1.02)86)×50−20S=−20×50×(1.02−(1.02)87)−20S=−1000×(1.02−(1.02)87)−20
Calculate power of 1.0287: Calculate the power of 1.0287. This step involves using a calculator or a computer to find the value of (1.02)87.
Substitute value of 1.0287: Substitute the value of (1.02)87 into the sum.Assuming the value of (1.02)87 is calculated correctly, substitute it back into the expression for S.S=−1000×(1.02−(1.02)87)−20
Complete calculation and round: Complete the calculation and round to the nearest integer.After finding the exact value of S, round it to the nearest integer to get the final answer.
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