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Recurring Decimals and Fractions

Recurring Decimals and Fractions

A recurring decimal can be converted to a fraction using powers of 10.

For example: `0. dot3 dot2` could be written as 0.3232323232....

Set x as 0.3232323232...

The number recurs every second digit.

Multiply both x and the number by 102 such that 100x = 32.32323232...

Subtract the original equation from the second equation:

100x = 32.32323232...

x = 0.3232323232.... , and subtract:

99x = 32, and make a fraction such that

`x = frac(32)(99)`.

If the number repeats every digit, multiply by 10; every third digit, multiply by 103 etc

Example 1

Convert `0.dot1 2 dot3` to a fraction.

`x` `= 0.123123123...`
Recurs every 3 digits `` ``
Multiply by 103 `1000x` `=123.123123123...`
Subtract equation `999x` `=123`
`x` `=frac(123)(999)`
Simplify: `x` `=frac(41)(333)`

Answer: `frac(41)(333)`

Example 2

Convert `2.dot4 dot5` to a fraction.

`x` `= 2.45454545...`
Recurs every 2 digits
Multiply by 102 `100x` `= 245.454545...`
Subtract `99x` `= 243`.
`x` `= frac(243)(99)`.
Simplify `x` `= 2frac(5)(11)`.

Answer: 2`frac(5)(11)`