2. Write the pure repeating (recurring) decimal number as an improper fraction.
99.9 can be written as an improper fraction.
- The numerator larger than or equal to the denominator.
Set up the first equation.
- Let y equal the decimal number:
y = 99.9
Set up the second equation.
- Number of decimal places repeating: 1
Multiply both sides of the first equation by 101 = 10
y = 99.9
10 × y = 10 × 99.9
10 × y = 999.9
Subtract the first equation from the second one.
- Having the same number of decimal places ...
- The repeating pattern drops off by subtracting the two equations.
10 × y - y = 999.9 - 99.9 ⇒
(10 - 1) × y = 999.9 - 99.9 ⇒
We now have a new equation:
9 × y = 900
Solve for y in the new equation.
9 × y = 900 ⇒
y = 900/9
Let the result written as a fraction.
Now we can write the number as a fraction.
According to our first equation:
y = 99.9
According to our calculations:
y = 900/9
⇒ 99.9 = 900/9
3. Reduce (simplify) the fraction above:
900/9
to the lowest terms, to its simplest equivalent form, irreducible.
To reduce a fraction to the lowest terms divide the numerator and denominator by their greatest (highest) common factor (divisor), GCF.
Factor the numerator and denominator (prime factorization).
900 = 22 × 32 × 52
9 = 32
Calculate the greatest (highest) common factor (divisor), GCF.
Multiply all the common prime factors by the lowest exponents.
GCF (22 × 32 × 52; 32) = 32
Divide both the numerator and the denominator by their GCF.
900/9 =
(22 × 32 × 52)/32 =
((22 × 32 × 52) ÷ 32) / (32 ÷ 32) =
(22 × 52)/1 =
100/1
Note:: 100/1 = 100