Measurement Adding and Subtracting Fractions with Different Denominators

 We can add fractions with the same (common) denominator easily. Adding and Subtracting Fractions =

 We can add fractions with the same (common) denominator easily. Adding and Subtracting Fractions =

 We can also add fractions without the same denominators by using equivalent fractions to determine a common denominator. Adding and Subtracting Fractions ? =

 Before we can add fractions, we need these numbers to be the same. Adding and Subtracting Fractions ? =

 First:Check to see if the smaller will divide into the larger denominator.  If so: We only have to change one of the denominators. Adding and Subtracting Fractions ? =

 Example: 2 will divide into 4, so we can use 4 as the common denominator Adding and Subtracting Fractions ? =

 Multiply both the numerator and denominator by 2 Adding and Subtracting Fractions ? = x ? =

 Multiply both the numerator and denominator by 2 Adding and Subtracting Fractions ? = x = 3434

 What if: The smaller denominator will not divide into the larger denominator?  If not: We have to find a common multiple for a denominator. Adding and Subtracting Fractions ? =

 Check the multiples of 3 and 4.  3 = 3, 6, 9, 12, 15, 18, 21, 24  4 = 4, 8, 12, 16, 20, 24 Adding and Subtracting Fractions ? =

 12 is the lowest common multiple of 3 and 4  3 = 3, 6, 9, 12, 15, 18, 21, 24  4 = 4, 8, 12, 16, 20, 24 Adding and Subtracting Fractions ? =

 To make the denominator of the first fraction 12, multiply both the numerator and denominator by 3. Adding and Subtracting Fractions ? = x3 ? 12 +=

 To make the denominator of the first fraction 12, multiply both the numerator and denominator by 3. Adding and Subtracting Fractions ? = x =

 To make the denominator of the second fraction 12, multiply both the numerator and denominator by 4. Adding and Subtracting Fractions ? = x ? 12 =

 To make the denominator of the second fraction 12, multiply both the numerator and denominator by 4. Adding and Subtracting Fractions ? = x =

 We can now add the two fractions. Adding and Subtracting Fractions ? = = 7 12

 Try this one: Adding and Subtracting Fractions ? =

? = ? = x5 x3

Adding and Subtracting Fractions ? = = x5 x