# [SOLVED]decimal expansion to rational number

#### dwsmith

##### Well-known member
I am given the number $.334444\ldots$

So we have $0+33\times 10^{-2} + \sum\limits_{n=3}^{\infty}4\times 10^{-n}$

Is there a way to put this all together in one geometric series?

#### CaptainBlack

##### Well-known member
I am given the number $.334444\ldots$

So we have $0+33\times 10^{-2} + \sum\limits_{n=3}^{\infty}4\times 10^{-n}$

Is there a way to put this all together in one geometric series?
No, you sum the infinite geometric series, and add $$33/100$$. Or sum:

$$\sum\limits_{n=1}^{\infty}4\times 10^{-n}=(4/10)(10/9)$$

and subtract $$11/100$$

CB

#### chisigma

##### Well-known member
I am given the number $.334444\ldots$

So we have $0+33\times 10^{-2} + \sum\limits_{n=3}^{\infty}4\times 10^{-n}$

Is there a way to put this all together in one geometric series?
$\displaystyle .33444...= \frac{1}{3} + \frac{1}{900} = \frac{301}{900}= \frac{1}{100}\ \frac{301}{9}= \frac{301}{1000}\ \sum_{n=0}^{\infty} 10^{-n}$

Kind regards

$\chi$ $\sigma$