Adding and Subtracting Fractions Mastery
Year 7 Mathematics Building Fluency with Different Denominators UK National Curriculum
Learning Objectives
Add and subtract fractions with the same denominator confidently Find common denominators for fractions with different denominators Add and subtract fractions with different denominators Solve multi-step problems involving fraction operations Apply fraction skills to real-world contexts
Recap: Adding Fractions with Same Denominators
When denominators are the same, add the numerators Keep the denominator unchanged Example: 2/7 + 3/7 = 5/7 Always simplify your answer if possible Check: Does your answer make sense?
Quick Practice: Same Denominators
When denominators are the same, add the numerators Keep the denominator unchanged Example: 2/7 + 3/7 = 5/7 Always simplify your answer if possible Check: Does your answer make sense?
The Challenge: Different Denominators
What happens when denominators are different? Example: 1/3 + 1/4 = ? We cannot add directly! We need a common denominator Think: What number do both 3 and 4 divide into evenly?
Step-by-Step Method for Different Denominators
Worked Example: 2/5 + 1/3
Step 1: Find LCM of 5 and 3 LCM = 15 (5 × 3 = 15) Step 2: Convert to equivalent fractions 2/5 = 6/15 and 1/3 = 5/15 Step 3: Add numerators: 6/15 + 5/15 = 11/15 Step 4: Check if we can simplify (we can't!)
Subtraction Works the Same Way!
{"left":"Adding Fractions:\n1. Find common denominator\n2. Convert both fractions\n3. Add numerators\n4. Simplify if possible","right":"Subtracting Fractions:\n1. Find common denominator\n2. Convert both fractions\n3. Subtract numerators\n4. Simplify if possible"}
Your Turn: Mixed Practice
Solve these fraction problems: 1/2 + 1/6 = 3/4 - 1/3 = 2/3 + 1/5 = 5/6 - 1/4 = Show all working out! Extension: Create your own problem for a partner
Mastery Check: Can You Explain?
A student says: 'I got 3/7 when I added 1/3 + 1/4' What mistake did they make? How would you help them understand the correct method? What is the correct answer?