Grade 6

Grade 6Number SystemFractions


Addition and Subtraction of Fractions


Fractions represent parts of a whole. Learning how to add and subtract fractions is an important skill in the world of math. In this guide, we'll learn step by step about adding and subtracting fractions. Let's start by understanding what a fraction is.

Understanding fractions

A fraction has two parts: the numerator and the denominator. The numerator is the top number, and the denominator is the bottom number. For example, in the fraction 3/4, 3 is the numerator, and 4 is the denominator.

   ___3___ ← Part
  , 
   ‾‾‾4‾‾ ← every

The denominator tells us how many parts the whole is divided into, and the numerator shows how many parts we have. A fraction can represent values that are less than or greater than a whole.

Addition of fractions

To add fractions, they must have the same denominator. This shared denominator is called the "common denominator." Let's first look at how we can add fractions with the same denominator.

Adding fractions with the same denominators

If the fractions to be added have the same denominator, then add the numerators and keep the denominator the same.

For example, to add 1/4 and 2/4:

    1 2 1 + 2
   , 
    4 4 4
            = ³/₄

Adding fractions with different denominators

If the fractions have different denominators, follow these steps:

  1. Find a common denominator: Find the least common multiple (LCM) of the denominators.
  2. Convert each fraction: Adjust the fractions to have the same denominator by multiplying both the numerator and denominator by the required numbers.
  3. Add the numerators: Now that the denominators are the same, add the numerators.
  4. Subtract if necessary: Simplify the fraction to its simplest form.

Example: Add 1/3 and 1/6

Step 1: The denominators are 3 and 6. The LCM of 3 and 6 is 6.

Step 2: Change 1/3 to the denominator of 6 Multiply both the numerator and denominator by 2.

    1 × 2
  , 
    3 × 2 6

Which gives us: 2/6

Step 3: Add 2/6 and 1/6:

   2 1 2 + 1
  ,
   6 6 6
          = ³/₆

Step 4: Simplify 3/6 by dividing both the numerator and denominator by 3:

   3/3
, 
   6/3
      = 1/2

Subtraction of fractions

Subtracting fractions works the same as adding. Let's learn how to subtract fractions with the same and different denominators.

Subtracting fractions with the same denominators

If the fractions have the same denominator, you can directly subtract the numerators while keeping the denominator the same.

For example, subtract 3/4 from 5/4:

   5 3 5 - 3
  , 
   4 4 4
          = 2/4

Then simplify 2/4 by dividing both the numerator and denominator by 2:

   2/2
, 
   4/2
      = 1/2

Subtracting fractions with different denominators

If the fractions have different denominators, follow these steps:

  1. Find a common denominator: Find the least common multiple (LCM) of the denominators.
  2. Convert each fraction: Adjust the fractions to have the same denominator by multiplying both the numerator and denominator by the required numbers.
  3. Subtract fractions: Subtract the numerators because the denominators are the same.
  4. Subtract if necessary: Simplify the fraction to its simplest form.

Example: Subtract 2/5 from 3/4

Step 1: The denominators are 4 and 5. The LCM of 4 and 5 is 20.

Step 2: Convert 3/4 and 2/5 to the denominator of 20:

For 3/4 multiply both the numerator and denominator by 5:

    3 × 5
  , 
    4 × 5 20

Which gives us: 15/20

For 2/5 multiply both the numerator and denominator by 4:

    2 × 4
  , 
    5 × 4 20

Which gives us: 8/20

Step 3: Subtract 8/20 from 15/20:

  15 8 15 - 8
 , 
  20 20 20
          = 7/20

The fraction 7/20 is already in its simplest form.

Practice problems

Let's practice adding and subtracting fractions:

Add

  1. 2/7 + 3/7 = ?
  2. 3/8 + 1/4 = ?
  3. 4/5 + 2/9 = ?

Subtraction

  1. 5/12 - 1/12 = ?
  2. 7/10 - 2/5 = ?
  3. 11/15 - 4/15 = ?

Conclusion

Mastering the addition and subtraction of fractions takes practice, but it is essential to developing your mathematical skills. Start with questions with like denominators. Once you are comfortable, move on to questions with unequal denominators.

These concepts are fundamental skills that will help you in advanced math topics like algebra and geometry. Practice regularly and apply these techniques to solve real-world problems involving fractions.


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