Is 3.6363636363636363... an irrational number?

1 answer

No, \( 3.6363636363636363... \) is not an irrational number. It is a repeating decimal, which can be expressed as a fraction. The repeating part is "63," and so the number can be represented as:

\[ 3.6363636363... = 3 + 0.6363636363... \]

To convert \( 0.6363636363... \) into a fraction, let \( x = 0.6363636363... \). Then, by multiplying both sides by 100 (since the repeating part has two digits), we have:

\[ 100x = 63.6363636363... \]

Now, subtract the original equation from this one:

\[ 100x - x = 63.6363636363... - 0.6363636363... \] \[ 99x = 63 \] \[ x = \frac{63}{99} \]

This fraction can be simplified:

\[ x = \frac{63 \div 9}{99 \div 9} = \frac{7}{11} \]

Thus,

\[ 0.6363636363... = \frac{7}{11} \]

Now, we can combine this back into our original equation:

\[ 3.6363636363... = 3 + \frac{7}{11} = \frac{33}{11} + \frac{7}{11} = \frac{40}{11} \]

Since \( \frac{40}{11} \) is a fraction and not a whole number or an irrational number, we conclude that \( 3.6363636363... \) is a rational number.