1. 4-2 Adding and Subtracting Fractions
What You’ll Learn
To add fractions
To subtract fractions

2. Reduce the following
3/12 =
12/32 =
5/45 =
15/200 =
72/120 =

3. Example 1 Adding like Fractions: Solve: 3/8 + 4/8 = ?
Step 1: Rewrite the problem vertically.
Step 2: Add the numerators (the number above the line). The denominator (the number below the line) remains the same.
Step 3: Reduce if necessary

4. Example 2: Subtract like Fractions Solve: 6/12 - 5/12 = ?
Step 1: Rewrite the problem vertically.
Step 2: Subtract the numerators (the number above the line). The denominator (the number below the line) remains the same.
Step 3: Reduce if necessary

5. Find the LCM
3 & 4
12 & 4
5 & 100
6 & 20
8 & 78

6. Example 3: Adding Unlike Fractions : Solve 1/5 + 4/9 = ?
Step 1: Rewrite horizontal problems vertically. (This step is not necessary, but many students find it easier to add fractions when the problems are written vertically.)
Step 2: Find a common denominator (a common multiple of the denominators of two or more fractions). For this problem, the common denominator is 45, because 9 and 5 will both divide into 45.
Step 3: Multiply 1/5 by 9/9. Rewrite the first fraction as 9/45. Multiply 4/9 by 5/5. Rewrite the second fraction as 20/45.
Step 4: Add the numerators together ( = 29). The denominator (45) remains the same

7. Example 4: Subtracting Unlike Fractions Solve: 6/7 - 3/4 = ?
Step 1: Rewrite the problem vertically.
Step 2: Find a common denominator (a common multiple of the denominators). For this problem, the common denominator is 28. Multiply 6/7 by 4/4. Multiply 3/4 by 7/7.
Step 3: Rewrite 6/7 as 24/28. Rewrite 3/4 as 21/28.
Step 4: Subtract the numerators ( = 3). The denominator (28) remains the same.
Practice: Text page 194 # 1-23 odd

8. Try to Add or Subtract the Following
3/5 + 1/5 =
11/12 – ¼ =
¾ - 1/8 =
7/12 – 1/3 =
5/6 – 9/24 =

9. Using the Ray Method for Adding and Subtracting Unlike Fractions
Draw 3 Rays
Write the products at the arrows
Write products as shown and subtract
Simplify (if needed)
2 – 2
Assign Pr 4-2

10. Using the Ray Method for Adding and Subtracting Unlike Fractions
Draw 3 Rays
Write the products at the arrows
Write products as shown and add
Simplify (if needed)
2 – 2
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