Adding and Subtracting Fractions Number Sense 1.2

How to add/subtract fractions. In order to add/subtract fractions, the denominator must be the same. Example: ¼ + 2/4 = ¾ If the denominator is not the same, you must find the least common multiple of the denominators (This can also be called the Least Common Denominator).

Unlike Denominators: Step 1: Use the upside down cake method to determine the LCM Step 2: The LCM becomes the new denominator for each fraction. 3/8 + 1/6 = [8 6] 4 3 2  4  3 LCM = 24 2

3/8 1/6 Step 3: Determine what factor multiplies to make the LCM. Multiply the numerator by that factor. Step 4: Always simplify when possible 9/24 4/24 13/24

2/3 + 1/5 Four Square Method: Write the steps in you own words. 1) 2) 3) 4) 1 5 2 2 10 3 15 Denominator 3 Answer: 13/15

Practice Add. Answers: 1.) 2/3 + 1/5 2.) 4/9 + 1/3 3.) 3/7 + 1/3 4.) 1/2 + 3/8 5.) 3/8 + 1/4 1.) 13/15 2.) 7/9 3.) 16/21 4.) 7/8 5.) 5/8