2. Write the mixed repeating (recurring) decimal number as a proper fraction.
0.12121219 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 = 0.12121219
Set up the second equation.
- Number of decimal places repeating: 1
Multiply both sides of the first equation by 101 = 10
y = 0.12121219
10 × y = 10 × 0.12121219
10 × y = 1.2121219
Get the same number of decimal places as for y:
10 × y = 1.21212199
Note: 1.21212199 = 1.2121219
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 = 1.21212199 - 0.12121219 ⇒
(10 - 1) × y = 1.21212199 - 0.12121219 ⇒
We now have a new equation:
9 × y = 1.0909098
Solve for y in the new equation.
9 × y = 1.0909098 ⇒
y = 1.0909098/9
Let the result written as a fraction.
Now we can write the number as a fraction.
According to our first equation:
y = 0.12121219
According to our calculations:
y = 1.0909098/9
⇒ 0.12121219 = 1.0909098/9
Get rid of the decimal places in the fraction above.
- Multiply the top and the bottom number by 10,000,000.
- 1 followed by as many 0-s as the number of digits after the decimal point.
0.12121219 = (1.0909098 × 10,000,000)/(9 × 10,000,000)
0.12121219 = 10,909,098/90,000,000
3. Reduce (simplify) the fraction above:
10,909,098/90,000,000
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).
10,909,098 = 2 × 32 × 331 × 1,831
90,000,000 = 27 × 32 × 57
Calculate the greatest (highest) common factor (divisor), GCF.
Multiply all the common prime factors by the lowest exponents.
GCF (2 × 32 × 331 × 1,831; 27 × 32 × 57) = 2 × 32
Divide both the numerator and the denominator by their GCF.
10,909,098/90,000,000 =
(2 × 32 × 331 × 1,831)/(27 × 32 × 57) =
((2 × 32 × 331 × 1,831) ÷ (2 × 32)) / ((27 × 32 × 57) ÷ (2 × 32)) =
(331 × 1,831)/(26 × 57) =
606,061/5,000,000