Class 8 Maths – Chapter 8

Comparing Quantities

Final Revision Sheet

🔑 Key Concepts at a Glance

• Percentage (%) = Per hundred
• Profit = Selling Price (SP) − Cost Price (CP)
• Loss = Cost Price (CP) − Selling Price (SP)
• Discount = Marked Price (MP) − Selling Price (SP)
• Simple Interest (SI) = (P × R × T) ÷ 100
• Amount = Principal + Simple Interest

📐 Important Formulae

• Percentage = (Part ÷ Whole) × 100
• Profit % = (Profit ÷ CP) × 100
• Loss % = (Loss ÷ CP) × 100
• Discount % = (Discount ÷ MP) × 100
• SI = (P × R × T) ÷ 100

✏️ Quick Examples

1️⃣ Find 20% of 150
= (20 ÷ 100) × 150 = 30

2️⃣ CP = ₹500, SP = ₹550
Profit = 550 − 500 = ₹50

3️⃣ MP = ₹1000, Discount = ₹200
SP = 1000 − 200 = ₹800

4️⃣ P = ₹2000, R = 5%, T = 2 years
SI = (2000 × 5 × 2) ÷ 100 = ₹200

⚠️ Common Mistakes to Avoid

• Mixing up CP and SP
• Forgetting to divide by 100
• Using MP instead of CP for Profit %
• Missing ₹ symbol in money problems

📝 Exam Writing Tips

• Write formula first
• Show step-by-step calculation
• Box or underline final answer
• Maintain neat handwriting