10.3.54 repeating decimal + geometric series

In summary, the repeating decimal $6.94\overline{32}$ can be written as a geometric series with the sum starting at $6.94$ and the common ratio being $0.01$. It can also be written as a fraction, specifically $\frac{694}{100}+\frac{32}{9900}$ or as $\frac{34369}{4950}$. This can be found by using the formula for the sum of an infinite geometric series and manipulating it to fit the given decimal.
  • #1
karush
Gold Member
MHB
3,269
5
$\tiny{206.10.3.54}$
$\text{Write the repeating decimal first as a geometric series} \\$
$\text{and then as fraction (a ratio of two intergers)} \\$
$\text{Write the repeating decimal as a geometric series} $
$6.94\overline{32}=6.94323232 \\$
$\displaystyle A.\ \ \ 6.94\overline{32}=\sum_{k=0}^{\infty}6.94(0.1)^k \\$
$\displaystyle B.\ \ \ 6.94\overline{32}=0.0032+\sum_{k=0}^{\infty}6.94(0.001)^k \\$
$\displaystyle C.\ \ \ 6.94\overline{32}=6.94+\sum_{k=0}^{\infty}0.0032(0.01)^k$

chose c but guessed?
 
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  • #2
\(\displaystyle 6.94\overline{32}=\frac{694}{100}+\frac{32}{100}\cdot\frac{1}{99}=\frac{694}{100}+\frac{32}{10000}\cdot\frac{1}{1-\dfrac{1}{100}}=\frac{694}{100}+\frac{32}{100}\sum_{k=1}^{\infty}\left(\left(\frac{1}{100}\right)^k\right)=\frac{694}{100}+\frac{32}{10000}\sum_{k=0}^{\infty}\left(\left(\frac{1}{100}\right)^k\right)\)

This is equivalent to choice c).

\(\displaystyle 6.94\overline{32}=\frac{694}{100}+\frac{32}{9900}=\frac{34369}{4950}\)
 
  • #3
thanks couldn't find any example on how to do this one.
kinda strange prob!em😎
 

Related to 10.3.54 repeating decimal + geometric series

1. What is a repeating decimal?

A repeating decimal is a decimal number that has a pattern of digits that repeats infinitely. For example, 0.3333... is a repeating decimal with the pattern "3".

2. How do you convert a repeating decimal to a fraction?

To convert a repeating decimal to a fraction, you can set up an equation where the repeating decimal is equal to x, and then solve for x. For example, if the decimal is 0.4545..., you can set up the equation 0.4545... = x. Then, multiply both sides by 100 to get 45.45... = 100x. Subtract the two equations to get 99x = 45, and solve for x to get x = 45/99, which simplifies to 5/11.

3. What is a geometric series?

A geometric series is a series of numbers where each term is found by multiplying the previous term by a constant number, called the common ratio. The general form of a geometric series is: a, ar, ar^2, ar^3, ... where a is the first term and r is the common ratio.

4. How do you find the sum of a geometric series?

The formula for finding the sum of a finite geometric series is S = a(1-r^n) / (1-r), where S is the sum, a is the first term, r is the common ratio, and n is the number of terms. If the series is infinite, the sum can be found using the formula S = a / (1-r).

5. How do you find the sum of a geometric series when the first term is a repeating decimal?

To find the sum of a geometric series when the first term is a repeating decimal, you can first convert the decimal to a fraction, and then use the formula for finding the sum of a geometric series. For example, if the first term is 0.4545..., you can convert it to 5/11 and then use the formula S = a(1-r^n) / (1-r) to find the sum.

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