Math Problem Statement

Find the sum of the first 9 terms of the following series, to the nearest integer.

32, comma, 8, comma, 2, comma, point, point, .

32,8,2,

Solution

The given series is:

32,8,2,32, 8, 2, \dots

This is a geometric series because each term is obtained by multiplying the previous term by a common ratio rr. Let's determine the common ratio:

r=832=14r = \frac{8}{32} = \frac{1}{4}

So, the common ratio is 14\frac{1}{4}. The first term aa is 3232.

Formula for the sum of the first nn terms of a geometric series:

Sn=a(1rn)1rS_n = \frac{a(1 - r^n)}{1 - r} where:

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

For the first 9 terms:

  • a=32a = 32,
  • r=14r = \frac{1}{4},
  • n=9n = 9.

Substitute the values into the formula:

S9=32(1(14)9)114S_9 = \frac{32(1 - (\frac{1}{4})^9)}{1 - \frac{1}{4}}

Simplifying the denominator:

114=341 - \frac{1}{4} = \frac{3}{4}

So, the sum becomes:

S9=32(1(14)9)34=32×43×(11262144)S_9 = \frac{32(1 - (\frac{1}{4})^9)}{\frac{3}{4}} = \frac{32 \times 4}{3} \times \left(1 - \frac{1}{262144}\right)

S9=1283×(10.0000038)S_9 = \frac{128}{3} \times \left(1 - 0.0000038\right)

S91283×0.999996242.6667×0.999996242.6666S_9 \approx \frac{128}{3} \times 0.9999962 \approx 42.6667 \times 0.9999962 \approx 42.6666

Thus, the sum of the first 9 terms of the series, to the nearest integer, is:

43\boxed{43}

Would you like more details on any step or have any further questions?

Related questions:

  1. How do you find the common ratio of a geometric series?
  2. How would the formula for the sum change if the common ratio were negative?
  3. What is the sum of the first 5 terms of this series?
  4. How do you determine if a series is geometric?
  5. Can the sum formula be applied to infinite geometric series?

Tip:

In a geometric series, the sum converges only if the absolute value of the common ratio r<1|r| < 1.

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Math Problem Analysis

Mathematical Concepts

Geometric Series
Exponents
Series Summation

Formulas

Sum of the first n terms of a geometric series: Sn = a(1 - r^n) / (1 - r)

Theorems

Sum formula for a geometric series with |r| < 1

Suitable Grade Level

Grades 10-12