\[\frac{1}{27}-\frac{1}{9}\]

Choose Topic

Examples

Find the Least Common Denominator (LCD) of

\frac{1}{27},\frac{1}{9}

. In other words, find the Least Common Multiple (LCM) of

27,9

Method 1: By Listing Multiples

List the multiples of each number.

Multiples of 27

: 27, ...

Multiples of 9

: 9, 18, 27, ...

Find the smallest number that is shared by all rows above. This is the LCM.

LCM =

27

Method 2: By Prime Factors

List the prime factors of each number.

Prime Factors of 27

: 3, 3, 3

Prime Factors of 9

: 3, 3

Find the union of these primes.

3,3,3

Multiply these numbers:

3\times 3\times 3=27

. This is the LCM.

LCM =

27

To get access to all 'How?' and 'Why?' steps, join Cymath Plus!

LCD =

27

Make the denominators the same as the LCD.

\frac{1}{27}-\frac{1\times 3}{9\times 3}

Simplify. Denominators are now the same.

\frac{1}{27}-\frac{3}{27}

Join the denominators.

\frac{1-3}{27}

Simplify.

-\frac{2}{27}

Done

Decimal Form: -0.074074

Like this solution? Share it!