Calculating Percentages: Real-Life Discount Power
Year 7-8 Mathematics Lesson 2: Finding Percentages Real-world applications and discount calculations
Where Do You See Percentages?
Think about your daily life... Shopping centres and sales Sports statistics and scores Weather forecasts and humidity Battery levels on devices Test scores and grades
What Is a Percentage?
A percentage means 'out of 100' 50% = 50 out of 100 = 1/2 = 0.5 25% = 25 out of 100 = 1/4 = 0.25 Percentages help us compare parts to wholes The % symbol means 'per hundred'
Benchmark Percentages: Your Calculation Shortcuts
10% = divide by 10 (easy!) 5% = half of 10% 1% = divide by 100 50% = divide by 2 25% = divide by 4 These are your percentage 'building blocks'
Let's Calculate: 20% of $50
Method 1: Using 10% benchmark 10% of $50 = $5 20% = 2 × 10% = 2 × $5 = $10 Method 2: Using decimals 20% = 0.20 $50 × 0.20 = $10
Bar Models: Seeing Percentages Visually
Bar models help us visualize the problem The whole bar represents 100% We can divide it into percentage parts Great for checking if our answer makes sense Visual thinking supports understanding
Real Shopping Scenario
{"left":"Original price: $80 jacket\nDiscount: 25% off\nCalculate the discount amount\n25% of $80 = ?","right":"Method: 25% = 1/4\nSo $80 ÷ 4 = $20\nSale price: $80 - $20 = $60"}
Pair Practice: Discount Detective
Work with your partner Calculate these discounts: 15% off $200 headphones 30% off $60 shoes Show your working using benchmarks Check each other's answers Discuss which method you used
Hands-On Money Challenge
Use paper money to model discounts Start with $100 in notes Calculate 20% discount physically Remove the discount amount Count what's left - that's your sale price! Try different percentage discounts
Percentage Power: What We've Learned
Percentages are parts of 100 Benchmark percentages make calculations easier Two main methods: benchmarks and decimals Bar models help us visualize problems Always check if your answer makes sense Percentages are everywhere in real life!