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Simplifying Complex Fractions

 

When a "normal" fraction contains fractions in either the numerator or denominator, or both, then we consider it to be a complex fraction. This type of fraction is also known as compound fraction.

There are two methods used to simplify such kind of fraction.

 

Method 1 Method 2

Key steps:

  • Create a single fraction in the numerator and denominator.
  • Apply the division rule of fraction by multiplying the numerator by the reciprocal or inverse of the denominator.
  • Simplify, if necessary.

Key steps:

  • Find the Least Common Denominator (LCD) of all the denominators in the complex fractions.
  • Multiply this LCD to the numerator and denominator of the complex fraction.
  • Simplify, if necessary.

 

After going over a few examples, you should realize that Method 2 is much better than Method 1 because almost always it takes less number of steps to get to the final answer.

 


Example 1: Simplify the complex fraction [(2x^3)/(3y)]/[(x^2)/(6y)] .

Using Method 1

Both the numerator and denominator of the complex fraction are already expressed as single fractions. This is great!

shows where the complex numerator and complex denominator  are.

Next step to do is to apply division rule by multiplying the numerator by the reciprocal of the denominator. Finish off by cancelling out common factors to get the final answer.

[(2x^3)/(3y)]/[(x^2)/(6y)]=4x

Using Method 2

Find the LCD of the entire problem, that is, the LCD of the top and bottom denominators.

shows how to find the LCD of the complex denominators

Since the LCD of 3y and 6y is just 6y, we will now multiply the complex numerator and denominator by this LCD. After doing so, we can expect the problem to be reduced to a single fraction which can be simplified as usual.

multiply top and bottom by the LCD=6y.

 


 

Example 2: Simplify the complex fraction [1+(1/x)]/[1-(1/x^2)] .

Using Method 1

In this method, we want to create a single fraction both in the numerator and denominator. Obviously, this problem would require us to do that first before dividing.

Add the fractions in the numerator and subtract the ones in the denominator.

[1+(1/x)]/[1-(1/x^2)]=x/(x-1)

Using Method 2

Looking at the denominators x and x^2, its LCD must be x^2.  Multiply the top and bottom by this LCD.

multiply top and bottom by the LCD which is x^2 resulting to the simplified answer of x/(x-1)

 


Example 3: Simplify the complex fraction [(2/x)-(2/3x)]/[(1/x)-(5/6x)] .

Using Method 1

Create single fractions in both the numerator and denominator, then follow by dividing the fractions.

[(2/x)-(2/3x)]/[(1/x)-(5/6x)] = 8 after simplifying the compound fraction

Using Method 2

The overall LCD of the denominators is 6x. Use this to multiply through the top and bottom expressions.

[(2/x)-(2/3x)]/[(1/x)-(5/6x)] = 8/1

 


 

Example 4: Simplify the complex fraction hard problem  .

 

For this problem, we are going to use Method 1 only.

The problem requires you to apply the FOIL method (multiplication of two binomials) and a simple factorization of trinomial. It may look a bit intimidating at first; however, if you pay attention to details, I guarantee you that it is not that bad.

If you observe, the complex denominator is already in the form that we want - having one fractional symbol. This means we have to work a bit on the complex numerator. Our next step would be to transform the complex numerator into a "simple" or single fraction.

answer of the complicated compound fraction which is (x+1)/38(x+2)

 


Example 5: Simplify the complex fraction [(1/4x)+(1/3x)]/[(1/4x)-(1/3x)].

 

For this problem, we are going to use Method 2 only.

Observe that the LCD of all the denominators is just 12x. Use this as the common multiplier for both top and bottom expressions.

[(1/4x)+(1/3x)]/[(1/4x)-(1/3x)]=-7 after simplifying the compound fraction

 


 

Practice Problems with Answers
Worksheet 1 Worksheet 2

 

 

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