Math Problem Statement

Find the sum of 12 terms of the series 48, 24, 12...

Solution

The given series is:

48,24,12,48, 24, 12, \dots

This is a geometric series where the first term a1=48a_1 = 48 and the common ratio r=2448=12r = \frac{24}{48} = \frac{1}{2}.

The sum of the first nn terms of a geometric series is given by the formula:

Sn=a11rn1rS_n = a_1 \cdot \frac{1 - r^n}{1 - r}

For this series, we need to find the sum of the first 12 terms (S12S_{12}):

S12=481(12)12112S_{12} = 48 \cdot \frac{1 - \left(\frac{1}{2}\right)^{12}}{1 - \frac{1}{2}}

Let's compute this step by step:

  1. r12=(12)12=14096r^{12} = \left(\frac{1}{2}\right)^{12} = \frac{1}{4096}
  2. 1(12)12=114096=409614096=409540961 - \left(\frac{1}{2}\right)^{12} = 1 - \frac{1}{4096} = \frac{4096 - 1}{4096} = \frac{4095}{4096}
  3. S12=484095409612=48240954096=9640954096=393120409695.76S_{12} = 48 \cdot \frac{\frac{4095}{4096}}{\frac{1}{2}} = 48 \cdot 2 \cdot \frac{4095}{4096} = 96 \cdot \frac{4095}{4096} = \frac{393120}{4096} \approx 95.76

So, the sum of the first 12 terms is approximately:

95.76\boxed{95.76}

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

Here are 5 related questions for practice:

  1. What is the sum of the first 10 terms of the series 100,50,25,100, 50, 25, \dots?
  2. How can you find the sum of an infinite geometric series?
  3. What is the sum of the first 5 terms of the series 3,6,12,3, 6, 12, \dots?
  4. How do you find the common ratio in a geometric series?
  5. What is the sum of the first 15 terms of the series 80,40,20,80, 40, 20, \dots?

Tip: When calculating the sum of geometric series, be mindful of whether the common ratio is greater than or less than 1. It affects convergence for infinite series!

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Math Problem Analysis

Mathematical Concepts

Geometric Series
Summation of Series

Formulas

Sum of the first n terms of a geometric series: S_n = a_1 * (1 - r^n) / (1 - r)

Theorems

Geometric series summation

Suitable Grade Level

Grades 9-12