4. Convert .454545454545.......... (repeating decimal) to a rational number in simplest form.

1 answer

Let \( x = 0.454545454545 \ldots \).

To eliminate the repeating decimal, we can multiply both sides of the equation by 100, since the repeating part (45) has a length of 2 digits:

\[ 100x = 45.454545454545 \ldots \]

Now we have two equations:

  1. \( x = 0.454545454545 \ldots \)
  2. \( 100x = 45.454545454545 \ldots \)

Next, we can subtract the first equation from the second:

\[ 100x - x = 45.454545454545 \ldots - 0.454545454545 \ldots \]

This simplifies to:

\[ 99x = 45 \]

Now, we can solve for \( x \):

\[ x = \frac{45}{99} \]

Next, we simplify the fraction \( \frac{45}{99} \). We can find the greatest common divisor (GCD) of 45 and 99, which is 9.

Now we divide both the numerator and the denominator by their GCD:

\[ \frac{45 \div 9}{99 \div 9} = \frac{5}{11} \]

Thus, the repeating decimal \( 0.454545454545 \ldots \) can be expressed as the rational number in simplest form:

\[ \boxed{\frac{5}{11}} \]