Question

How you subtract with unlike Denominators

Answer 1

You must first find a common denominator. When the fractions have the same denominator, then you subtract the numerators and write the same denominator.

Example:

Subtract 3/4 - 1/8.

Solution:

The least common denominator of 4 and 8 is 8. Find an equivalent fraction to 3/4 with denominator 8. 3/4 = 3/4 * 2/2 = 6/8. 3/4 is equivalent to 6/8.

Now we replace 3/4 with its equivalent, 6/8.

3/4 - 1/8 =

= 6/8 - 1/8

Subtract the numerators: 6 - 1 = 5

Use the same common denominator in the answer.

= 6/8 - 1/8

= 5/8

The answer is 5/8

Answer 2

Explanation:

To subtract, you must first:

Find like denominators.

• Note: What you do to the denominator, you must do to the numerator.
• If there is an equal sign, and there are fractions on both side, what you do to one side, you do to the other.

Simplify:

• Combine like terms
• Solve

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Take for example, a question such as:

7 3/10 - 9/20

First, change the mixed fraction into improper fraction:

7 = (7/1) * (10/10) = 70/10 + 3/10 = 73/10

Find common denominators. Remember that what you do to the denominator, you do to the numerator. Multiply 2 to both numerator and denominator:

(73/10)(2/2) = (146/20)

Simplify. Combine like terms

146/20 - 9/20 = 137/20

Simplify.

137/20 = 6 17/20

6 17/20 would be your answer for the example question.

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