freeCodeCamp/guide/english/mathematics/adding-fractions/index.md

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Adding Fractions

Adding Fractions

A fraction is generally used to represent a number which is a ratio of two numbers.
Consider the fraction 45, here 4 is called the numerator and 5 is called the denominator.

Adding fractions with common denominator

Add the numerators of both fractions and put the resultant over the denominator.

Example 1

Consider fractions 45 and 35

  1. The denominator of the fractions is common.
  2. The numerators are 4 and 3
  3. Add the numerators, 4 + 3 = 7
  4. Place the resultant over the common denominator
  5. Simplify the resultant fraction, if possible
  45 + 35 = 75 
Example 2
  516 + 316 = 816 (Simplifying it further, 816 = 12) 

Adding fractions with different denominators

  1. Convert the fractions to equivalent fractions with common denominator

  2. To convert two fractions to common denominator, multiply the numerator and denominator of a fraction with the denominator of the other fraction.

  3. Now that the fractions have common denominators, add the numerators of both fractions and put the resultant over the denominator

    Consider, ab and cd are fractions with different denominators, you can add these fractions in a single step like below,

  ab + cd = (a * d) + (b * c)(b * d) 
Example

Consider fractions 56 and 515

  1. The denominators are different. So you need to make the denominators common
  2. Before that, if possible, simplify the fractions. In this case, 515 can be simplified as 13. Here 515 and 13 are called equivalent fractions.
  3. After simplification, the fractions are 56 and 13.
  4. Now to add these fractions, you must make the denominators common
  5. Multiply the numerator and denominator of a fraction with denominator of the other
  6. For fraction 56 , the denominator of the other fraction is 3. For fraction 13 , the denominator of the other fraction is 6
  ((5 * 3) + (1 * 6))(6 * 3) = 2118 
  1. The resultant fraction is 2118. This can be further simplified as 76
  56 + 515 = 76 

76 is equivalent to 1 and 16