DI Tables: Speed Calculation Techniques

Reading Tables Efficiently

Step 1: Understand Structure (30 seconds)

• Row headers: Categories
• Column headers: Time periods/Attributes
• Units: Lakhs, Crores, Percentages
• Totals: Row totals, Column totals

Step 2: Identify Patterns

• Increasing/Decreasing trends
• Maximum/Minimum values
• Outliers

Common Calculations

Percentage

• Part/Whole × 100
• Percentage change = [(New - Old)/Old] × 100

Ratios

• Simplify before calculating
• Use approximations

Averages

• Sum / Count
• Weighted average when needed

Speed Techniques

Approximation

• 47/98 ≈ 50/100 = 50%
• 2347 + 4821 ≈ 2300 + 4800 = 7100

Percentage Shortcuts

• 10% = Divide by 10
• 5% = Half of 10%
• 15% = 10% + 5%
• 25% = Divide by 4

Ratio Comparison

• Cross multiply: a/b vs c/d → Compare ad vs bc

CAT-Specific Tips

• Don't calculate everything - answer only what's asked
• Use options to backtrack
• Mark easy questions first
• Time: 3-4 minutes per question set

Practice Strategy

• Start with 2-variable tables
• Progress to 3-4 variable tables
• Practice mental calculation daily