Mental Multiplication and Division Strategies
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Mental Multiplication and Division Strategies
WALT: Explore and choose appropriate mental methods Using powers of ten and splitting strategies Year 7 Mathematics - 45 minutes
WALT & Success Criteria
WALT: Explore and choose appropriate mental multiplication and division methods Success Criteria: ✓ I can multiply numbers by powers of 10 ✓ I can divide numbers by powers of 10 ✓ I can use different mental methods to solve problems
Powers of 10 - The Pattern
10¹ = 10 10² = 100 10³ = 1,000 10⁴ = 10,000 Notice: The exponent tells us how many zeros! Quick rule: Count the zeros = the power
Quick Fire: Multiply by Powers of 10
Try these mentally: 23 × 10 = ? 45 × 100 = ? 7 × 1,000 = ? Strategy: Add zeros or move decimal point right
Division by Powers of 10
Division is the opposite of multiplication 4,500 ÷ 10 = 450 4,500 ÷ 100 = 45 4,500 ÷ 1,000 = 4.5 Strategy: Remove zeros or move decimal point left
Mental Strategies Comparison
{"left":"Splitting Method: 24 × 15 = 24 × 10 + 24 × 5 = 240 + 120 = 360\nDoubling Method: 16 × 25 = 16 × 50 ÷ 2 = 800 ÷ 2 = 400","right":"Powers of 10: 37 × 200 = 37 × 2 × 100 = 74 × 100 = 7,400\nNear Numbers: 23 × 19 = 23 × 20 - 23 × 1 = 460 - 23 = 437"}
Choose Your Strategy Challenge
Solve using ANY mental method: Level 1: 12 × 10, 60 ÷ 10 Level 2: 25 × 100, 450 ÷ 10 Level 3: 18 × 15, 240 ÷ 12 Level 4: 23 × 99, 750 ÷ 25 Extension: Create your own problem!
Reflection & Next Steps
"Mathematics is not about numbers, equations, or algorithms: it is about understanding." - William Paul Thurston Today we learned to: ✓ Use powers of 10 efficiently ✓ Choose appropriate mental strategies ✓ Support each other's learning (ako) Next lesson: Applying these strategies to real-world problems