Math Problem Statement

Evaluate the summation \( \sum_{n=2}^{47} 40(0.96)^{n-2} \)

Solution

The image shows a summation (Σ) notation:

n=24740(0.96)n2\sum_{n=2}^{47} 40(0.96)^{n-2}

This is a geometric series where the terms are given by 40(0.96)n240(0.96)^{n-2}, and the summation runs from n=2n = 2 to n=47n = 47.

Step-by-step breakdown:

  1. General term: The general term of the series is 40(0.96)n240(0.96)^{n-2}.
  2. Number of terms: The sum goes from n=2n = 2 to n=47n = 47, so there are 472+1=4647 - 2 + 1 = 46 terms in the series.
  3. First term: The first term when n=2n = 2 is 40(0.96)22=40(0.96)0=4040(0.96)^{2-2} = 40(0.96)^0 = 40.
  4. Common ratio: The common ratio rr is 0.960.96, since each term is multiplied by 0.960.96 as nn increases.

This series is geometric, and the sum of a geometric series can be computed using the formula:

Sn=a1rn1rS_n = a \frac{1 - r^n}{1 - r}

Where:

  • aa is the first term,
  • rr is the common ratio,
  • nn is the number of terms.

Let's compute the sum using the provided values:

  • a=40a = 40,
  • r=0.96r = 0.96,
  • n=46n = 46.

I'll calculate the sum.The sum of the geometric series is approximately 847.08847.08.

Would you like further details or have any questions about the calculation?

Here are five related questions that might interest you:

  1. How does the formula for the sum of a geometric series change if the common ratio rr is greater than 1?
  2. What happens if the common ratio rr is negative?
  3. Can you compute the sum of an infinite geometric series?
  4. How does changing the number of terms nn affect the total sum?
  5. Could this series be used to model real-world problems, such as depreciation or discounting?

Tip: In a geometric series, if r<1|r| < 1, the series converges as nn approaches infinity, and the sum can be calculated using a simpler formula for infinite series.

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Math Problem Analysis

Mathematical Concepts

Geometric Series
Summation
Exponential Decay

Formulas

Sum of a geometric series: S_n = a (1 - r^n) / (1 - r)

Theorems

Geometric series sum theorem

Suitable Grade Level

Grades 10-12