Adding and subtracting fractions and mixed numbers Bits and Pieces II

Adding Fractions Like fractions are fractions with the same denominator. You can add like fractions easily by adding the numerators and writing the sum over the common denominator. NEVER add the denominators! Example: 1/5 + 2/5 = 3/5 Now try to add 4/10 + 2/10. Remember to simplify if possible!

Adding Fractions (cont.) Before you can add or subtract fractions with different denominators, you must first write the fractions as equivalent fractions with the same denominator. To find the least common denominator: Find the least common multiple (LCM) of both numbers. Rewrite the fractions as equivalent fractions with the LCM as the denominator. Let’s rewrite 3/4 and 1/3 so that they have the same denominator. Then, let’s add the two fractions.

Subtracting Fractions To subtract like fractions, keep the denominator and subtract the numerators. NEVER subtract the denominators! Let’s practice. 5/8- 1/8 Remember to simplify!

Subtracting fractions (cont.) To subtract fractions with different denominators, rewrite the fractions as equivalent fractions with the same denominator. Remember, to find the least common denominator, you look for the least common multiple of the numbers. Let’s practice. 11/20- 1/5

Adding Mixed Numbers To add mixed numbers: Find the least common denominator. Rewrite the fractions. Add the fractions. Add the whole numbers. Write your answer in lowest terms. Remember to make sure that the fraction is not improper. Let’s practice. 3 1/6 + 2 5/12

Subtracting Mixed Numbers To subtract mixed numbers: Find the least common denominator. Rewrite the fractions. Subtract the fractions. Subtract the whole numbers. Write your answer in lowest terms. Let’s practice. 44/5 – 31/3

Subtracting Mixed Numbers (cont.) Sometimes you have to subtract a mixed number that has a greater fraction from a mixed number with a smaller fraction. Ex: 3 1/8 – 1 3/8 What do you do in this case? There are two options. You can either change both mixed numbers to improper fractions to subtract, or you can borrow a whole from the 3, and add the whole to the 1/8 as 8/8. Now you have 2 9/8 – 1 3/8. Let’s try.