2. Write the mixed repeating (recurring) decimal number as a proper fraction.
0.1212121215 can be written as a proper fraction.
- The numerator is smaller than the denominator.
Set up the first equation.
- Let y equal the decimal number:
y = 0.1212121215
Set up the second equation.
- Number of decimal places repeating: 1
Multiply both sides of the first equation by 101 = 10
y = 0.1212121215
10 × y = 10 × 0.1212121215
10 × y = 1.212121215
Get the same number of decimal places as for y:
10 × y = 1.2121212155
Note: 1.2121212155 = 1.212121215
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 = 1.2121212155 - 0.1212121215 ⇒
(10 - 1) × y = 1.2121212155 - 0.1212121215 ⇒
We now have a new equation:
9 × y = 1.090909094
Solve for y in the new equation.
9 × y = 1.090909094 ⇒
y = 1.090909094/9
Let the result written as a fraction.
Now we can write the number as a fraction.
According to our first equation:
y = 0.1212121215
According to our calculations:
y = 1.090909094/9
⇒ 0.1212121215 = 1.090909094/9
Get rid of the decimal places in the fraction above.
- Multiply the top and the bottom number by 1,000,000,000.
- 1 followed by as many 0-s as the number of digits after the decimal point.
0.1212121215 = (1.090909094 × 1,000,000,000)/(9 × 1,000,000,000)
0.1212121215 = 1,090,909,094/9,000,000,000
3. Reduce (simplify) the fraction above:
1,090,909,094/9,000,000,000
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).
1,090,909,094 = 2 × 11 × 4,723 × 10,499
9,000,000,000 = 29 × 32 × 59
Calculate the greatest (highest) common factor (divisor), GCF.
Multiply all the common prime factors by the lowest exponents.
GCF (2 × 11 × 4,723 × 10,499; 29 × 32 × 59) = 2
Divide both the numerator and the denominator by their GCF.
1,090,909,094/9,000,000,000 =
(2 × 11 × 4,723 × 10,499)/(29 × 32 × 59) =
((2 × 11 × 4,723 × 10,499) ÷ 2) / ((29 × 32 × 59) ÷ 2) =
(11 × 4,723 × 10,499)/(28 × 32 × 59) =
545,454,547/4,500,000,000