Subtracting Fractions (with common or uncommon denominators)

Subtracting Fractions with Common Denominators

When we subtract fractions that have the same, or common denominators, we subtract only the numerators. The denominators stay the same.

Example :

The following video shows how to subtract fractions with common denominators.

Subtracting Fractions With Uncommon Denominators

To subtract fractions with uncommon denominators, we need to change the fractions to equivalent farctions with common denominators before we find the difference.

First, we would need to find the least common denominator (LCD), which is the LCM of the denominators.

Next, we write equivalent fractions using the least common denominator. Then, we proceed to subtract as before.

Example:

Evaluate

Solution:

Step 1 : Find the LCD or LCM of 2 and 5

Multiples of 2: 2, 4, 6, 8, 10, 12

Multiples of 5: 5, 10, 15

The LCD or the Least Common Multiple of 2 and 5 is 10

Step 2 : Write both fractions as equivalent fractions with a common denominator of 10.

Step 3: Subtract the 2 equivalent fractions.

The following video shows how to subtract fractions with uncommon denominators.

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