Case Interview Math Fundamentals

Introduction

• Importance of math in case interviews
• Six fundamental math concepts
• Five types of case interview math questions
• Tips to excel in case interview math

Six Fundamental Math Concepts

1. Fractions
   • Simplification, addition, subtraction, multiplication, division
   • Examples:
     • Simplification: ( \frac{36}{54} = \frac{2}{3} )
     • Addition: ( \frac{1}{3} + \frac{1}{4} = 7/12 )
     • Subtraction: ( \frac{1}{3} - \frac{1}{4} = 1/12 )
     • Multiplication: ( \frac{3}{4} \times \frac{4}{9} = \frac{1}{3} )
     • Division: ( \frac{3}{4} \div \frac{9}{2} = \frac{1}{6} )
2. Decimals
   • Addition, subtraction, multiplication, division
   • Scientific notation
   • Examples:
     • Addition: 1.21 + 3.5 = 4.71
     • Subtraction: 14.2 - 8.05 = 6.15
     • Multiplication: 1.12 * 5 = 5.6
     • Division: 14.7 / 4.2 = 3.5
3. Percentages
   • Conversion, percent change
   • Example: New gas price = $3.60, old price = $3; Percent change = 20%
4. Ratios and Proportions
   • Ratios, proportion calculations
   • Example: 45 workers, 6 supervisors
5. Basic Statistics
   • Mean/average, weighted average, standard deviation, expected value
   • Calculations:
     • Average labor cost: $12/hour
     • Weighted average: 32%
     • Expected value: $72 million
6. Algebraic Equations
   • Solving for unknowns
   • Example: Revenue this year = $100 million, growth = 60%, last year revenue = $62.5 million*

Five Types of Math Questions

1. Profit and Break Even Questions
   • Revenue, costs, profit
   • Profit formulas and examples
   • Break-even analysis: 50,000 pizzas for break-even
2. Investment Questions
   • ROI, payback period
   • Examples:
     • Payback period: 5 years
     • ROI: 30%
3. Operations Questions
   • Output, utilization calculations
   • Examples:
     • Daily production: 1,200 cars
     • Efficiency: 75%
4. Charts and Graphs Questions
   • Types: bar charts, pie charts, line graphs, etc.
   • Example: Analyze and read axes out loud
5. Market Sizing Questions
   • Top-down and bottom-up approaches
   • Example: US tire market = $9.6 billion

Five Case Interview Math Tips

1. Develop a Structure
   • Approach and confirm steps before calculations
2. Round Numbers
   • Use round figures to simplify math
3. Use Abbreviations for Large Numbers
   • e.g., 10K for 10,000; 200M for 200 million
4. Rule of 72 for Growth Estimation
   • 72 / growth rate = years to double
5. Sense Check Numbers
   • Ensure calculations make sense at each step

Conclusion

• Practice essential to improve math skills
• Check resources for further practice and guided learning

Additional Resources

• Video link on solving case interviews in 30 minutes
• Comprehensive case interview course and books