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  1. $.\overline{36}=\frac{36}{99}$
  2. $2.1\overline{36}=2\frac3{22}$

The part I do not understand however, is "you could used 1) to speed up the working of 2)" which is written in the book.

How would I use 1) to help me work out 2)?

Thanks.

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$\frac3{22}=.1\overline{36}\text{ not } .1\overline{39}$ –  lab bhattacharjee May 5 '13 at 15:03
    
my bad, both were .36 not .39. –  user2121482 May 5 '13 at 15:09

2 Answers 2

up vote 3 down vote accepted

$$2.1\overline{39}=2+0.1+\frac1{10}\cdot0.\overline{39}$$

So, $$2.1\overline{39}=2+\frac1{10}+\frac1{10}\cdot\frac{36}{99}=2+\frac1{10}\cdot\left(1+\frac4{11}\right)=2+\frac1{10}\cdot\frac{15}{11}=2+\frac3{22}$$

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I've probably missed something here, but would that not = 2.239? –  user2121482 May 5 '13 at 15:13
    
@user2121482, please find the edited answer –  lab bhattacharjee May 5 '13 at 15:15
    
thanks. really confused at first (for example where the 4/11 came from), however it was my own bad since i had confused .39 with .36. –  user2121482 May 5 '13 at 15:47
    
how did you get 15/11? –  user2121482 May 5 '13 at 16:13
    
@user2121482, $$1+\frac4{11}=\frac{11+4}{11}=\frac{15}{11}$$ and cancelling out $9$ from the numerator & the denominator, $$\frac{36}{99}=\frac4{11}$$ –  lab bhattacharjee May 5 '13 at 16:14
  1. $.\overline{36}=\frac{36}{99}$
  2. $2.1\overline{36}=2\frac3{22}$

part 1.

suppose $$\begin {equation}\dfrac pq=0.\overline{36}\end {equation}$$ this is eqn (1).

mulipltly this eqn with 100 $$\begin {equation}100\dfrac pq=36.\overline{36}\end {equation}$$ this is eqn (2).Now subtract (1) from (2). $$\begin {equation}100\dfrac pq-\frac pq=36.\overline{36}-0.\overline{36}\end {equation}$$ $$99\dfrac pq=36.0$$ $$\dfrac pq=\frac {36}{99}$$

part 2

$2.1\overline{36}=2+0.1\overline{36}$ $$\dfrac pq=0.1\overline{36}\implies 10\dfrac pq=1.\overline{36}$$this is eqn (1).

multilpy with 100 in eqn(1) $$1000\dfrac pq=136.\overline{36}$$ then subtract (1) from (2). $$990\dfrac pq=135.0$$ $$\dfrac pq=\dfrac {135}{990}\implies\dfrac {3}{22}$$

so $2.1\overline{36}\implies 2+0.1\overline{36}\implies 2+\dfrac{3}{22}\implies 2\dfrac3{22}$

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