To convert the repeating decimal \( 0.09\overline{9} \) into a rational number, we can follow these steps.
Let \( x = 0.09\overline{9} \). This means that \( x = 0.099999...\).
To isolate the repeating part, we can multiply \( x \) by a power of 10 that moves the decimal point to the right, placing the repeating part as the leading part.
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Multiply by 10: \[ 10x = 0.99999... \]
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Now, create another equation by multiplying \( x \) by 100: \[ 100x = 9.99999... \]
Now, we have two equations:
- \( 10x = 0.99999... \) (1)
- \( 100x = 9.99999... \) (2)
Next, we can subtract equation (1) from equation (2).
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Subtract the two equations: \[ 100x - 10x = 9.99999... - 0.99999... \] \[ 90x = 9 \]
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Solve for \( x \): \[ x = \frac{9}{90} \]
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Simplify the fraction: \[ x = \frac{1}{10} \]
Thus, the rational number in simplest form that represents \( 0.09\overline{9} \) is \(\frac{1}{10}\).