Write the following infinite decimal expansion as a fraction. You do not need to simplify.

0.666...0.666...0.666...

1 answer

To express the repeating decimal \( 0.666\ldots0.666\ldots0.666\ldots \) as a fraction, we need to identify the repeating part.

Let's denote the decimal expansion as \( x \): \[ x = 0.666\ldots \]

The digit "6" repeats after the decimal indefinitely. To convert this repeating decimal into a fraction, we can set up the following equation:

  1. Multiply \( x \) by 10 (to shift the decimal point to the right): \[ 10x = 6.666\ldots \]

  2. Now, set up the equation using the original \( x \): \[ 10x = 6 + x \]

  3. Rearranging this gives: \[ 10x - x = 6 \] \[ 9x = 6 \]

  4. Solving for \( x \) yields: \[ x = \frac{6}{9} \]

This fraction can be simplified. However, you mentioned that simplification is not needed, so we can simply state the infinite decimal expansion as a fraction without simplification:

\[ \frac{6}{9} \]

Thus, the repeating decimal \( 0.666\ldots0.666\ldots0.666\ldots \) can be expressed as the fraction \( \frac{6}{9} \).