1. The problem is to find the percentage increase or decrease in various scenarios. 2. The formula for percentage change is: $$\text{Percentage Change} = \frac{\text{New Value} - \text{Old Value}}{\text{Old Value}} \times 100\%$$ 3. Important rules: - If the new value is greater than the old value, the percentage change is an increase. - If the new value is less than the old value, the percentage change is a decrease. 4. Example question 1: If the price of a commodity increases from 200 to 250, find the percentage increase. 5. Solution: $$\text{Percentage Increase} = \frac{250 - 200}{200} \times 100 = \frac{50}{200} \times 100 = 25\%$$ 6. Example question 2: If the population of a town decreases from 5000 to 4500, find the percentage decrease. 7. Solution: $$\text{Percentage Decrease} = \frac{5000 - 4500}{5000} \times 100 = \frac{500}{5000} \times 100 = 10\%$$ 8. Example question 3: A salary increases from 12000 to 14400. Find the percentage increase. 9. Solution: $$\text{Percentage Increase} = \frac{14400 - 12000}{12000} \times 100 = \frac{2400}{12000} \times 100 = 20\%$$ 10. Example question 4: The value of a car decreases from 800000 to 720000. Find the percentage decrease. 11. Solution: $$\text{Percentage Decrease} = \frac{800000 - 720000}{800000} \times 100 = \frac{80000}{800000} \times 100 = 10\%$$ 12. Example question 5: The price of sugar increases from 40 to 44. Find the percentage increase. 13. Solution: $$\text{Percentage Increase} = \frac{44 - 40}{40} \times 100 = \frac{4}{40} \times 100 = 10\%$$ 14. Example question 6: The number of students in a class decreases from 60 to 54. Find the percentage decrease. 15. Solution: $$\text{Percentage Decrease} = \frac{60 - 54}{60} \times 100 = \frac{6}{60} \times 100 = 10\%$$ 16. Example question 7: A shopkeeper increases the price of an item from 150 to 165. Find the percentage increase. 17. Solution: $$\text{Percentage Increase} = \frac{165 - 150}{150} \times 100 = \frac{15}{150} \times 100 = 10\%$$ 18. Example question 8: The population of a city decreases from 1,200,000 to 1,140,000. Find the percentage decrease. 19. Solution: $$\text{Percentage Decrease} = \frac{1200000 - 1140000}{1200000} \times 100 = \frac{60000}{1200000} \times 100 = 5\%$$ 20. Example question 9: The price of petrol increases from 90 to 99. Find the percentage increase. 21. Solution: $$\text{Percentage Increase} = \frac{99 - 90}{90} \times 100 = \frac{9}{90} \times 100 = 10\%$$ 22. Example question 10: The number of employees in a company decreases from 500 to 475. Find the percentage decrease. 23. Solution: $$\text{Percentage Decrease} = \frac{500 - 475}{500} \times 100 = \frac{25}{500} \times 100 = 5\%$$