Calculate the sum for the infinite geometric series

In summary, the sum for the infinite geometric series $4+2+1+\frac{1}{2}+...$ with a ratio of $\frac{1}{2}$ can be calculated using the formula $\displaystyle\sum_{n= 0}^{\infty}a{r}^{n}= a (\frac{1}{1-r})$, where $a=4$. This results in a sum of 8.
  • #1
karush
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Calculate the sum for the infinite geometric series
$4+2+1+\frac{1}{2}+...$

all I know is the ratio is $\frac{1}{2}$

$\displaystyle\sum_{n}^{\infty}a{r}^{n}$
assume this is used
 
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  • #2
karush said:
Calculate the sum for the infinite geometric series
$4+2+1+\frac{1}{2}+...$

all I know is the ratio is $\frac{1}{2}$

$\displaystyle\sum_{n}^{\infty}a{r}^{n}$
assume this is used

what is sum of Geometric series$\displaystyle\sum_{n= 0}^{\infty}a{r}^{n}= a (\frac{1}{1-r})$
using above
$= 4 (\frac{1}{1-\frac{1}{2}})= 4 * 2 = 8$
 
  • #3
Calculate the sum for the infinite geometric series
$4+2+1+\frac{1}{2}+...$

$a=4 \ \ r=\frac{1}{2}$

$\displaystyle\sum_{n= 0}^{\infty}a{r}^{n}= a (\frac{1}{1-r})
= 4 (\frac{1}{1-\frac{1}{2}})= 4 * 2 = 8$
 
  • #4
karush said:
Calculate the sum for the infinite geometric series
$4+2+1+\frac{1}{2}+...$

$a=5 \ \ r=\frac{1}{2}$

$\displaystyle\sum_{n= 0}^{\infty}a{r}^{n}= a (\frac{1}{1-r})
= 4 (\frac{1}{1-\frac{1}{2}})= 4 * 2 = 8$

$a = 4$ and not 5
 
  • #5
Saw it, got it
 

Related to Calculate the sum for the infinite geometric series

1. What is an infinite geometric series?

An infinite geometric series is a series of numbers that continues on infinitely, with each number being multiplied by a common ratio. It can be represented as a + ar + ar^2 + ar^3 + ..., where a is the first term and r is the common ratio.

2. How do you calculate the sum of an infinite geometric series?

The sum of an infinite geometric series can be calculated using the formula a/(1-r), where a is the first term and r is the common ratio. This formula only works if the absolute value of r is less than 1, otherwise the series will not converge.

3. Can an infinite geometric series have a finite sum?

Yes, an infinite geometric series can have a finite sum if the absolute value of the common ratio is less than 1. If the absolute value is greater than or equal to 1, the series will not converge and will have an infinite sum.

4. What is the difference between a finite and infinite geometric series?

A finite geometric series has a finite number of terms, while an infinite geometric series has an infinite number of terms. A finite geometric series can have a finite or infinite sum depending on the value of the common ratio, while an infinite geometric series will always have a finite sum if the common ratio is less than 1.

5. How is an infinite geometric series used in real life?

Infinite geometric series are commonly used in finance and economics to calculate compound interest, where the common ratio represents the interest rate. They are also used in physics and engineering to model exponential growth and decay processes. Additionally, infinite geometric series are used in computer algorithms and data compression techniques.

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