Lesson 4/5

Learning Intention: WALT to add fractions with different denominators by finding a common denominator.

Success Criteria:

• I can find a common denominator

• I can change fractions so they have the same denominator

• I can add the fractions and simplify the answer

Do Now – On the board: Solve:

• 2/5 + 1/5

• 3/8 + 4/8

• What are denominators? What does it mean to have a common denominator?

• We can only add fractions directly when they have the same denominator

• When they don’t, we need to change them so they do

How to find a common denominator by either changing one or both fractions

🟩 Example 1: Only one fraction needs to change

Problem:
1/4+1/2=

Step 1: Look at the denominators (4 and 2)
Can we make one denominator match the other? Yes! 2 can become 4.

Step 2: Rewrite 1/2 with denominator of 4
1/2=2/4

Step 3: Add
1/4+2/4=3/4

Key Idea:
Only the second fraction changed. We found an equivalent fraction.

🟦 Example 2: Both denominators need to change

Problem:
1/3+1/4=

Step 1: Denominators are 3 and 4.
No easy match—need to find a common denominator.

Step 2: Find the a Common Denominator of 3 and 4. An easy way is to multiply them by each other eg. 3x4= 12
Now change both fractions:

• 1/3=4/12

• 1/4=3/12

Step 3: Add
4/12+3/12=7/12

Today, we’re going to roll the dice and create our own fraction addition equations!

📝 Here’s How We’ll Do It:

1. Roll a ten-sided dice two times.

   • Use the larger number as the denominator (the bottom number).

   • Use the smaller number as the numerator (the top number)

   • This gives you your first fraction.

2. Roll the dice two more times to create your second fraction.

3. Now write an addition equation using both fractions!
   
   

Example:

If you roll a 3 and a 6, and then a 7 and a 3,
you would make this equation:
3/6 + 3/7 = ?

4. Solve your equation by finding a common denominator.