Tech Math Channel: Calculating Percentages in Your Head

Introduction

• Host: Josh
• Topic: An easy trick to calculate percentages mentally
• Example: Calculate 61% of 80
  • Expected method: 61/100 × 80
  • Trick: Simplifies calculation by dividing by 10 twice

Understanding Percentages

• Percentage Symbol (%): Means "per 100"
  • Per: Divided by
  • Cent: 100
• Traditional Calculation
  • Formula: (Percentage / 100) × Number

Simplified Method for Mental Calculation

1. Trick: Divide by 10 twice instead of 100
2. Example Calculation
   • 61% of 80
     • Divide 80 by 10: 80/10 = 8
     • Divide 61 by 10: 61/10 = 6.1
     • Multiply: 6 × 8 = 48
     • Add: 0.1 × 8 = 0.8
     • Final Answer: 48 + 0.8 = 48.8

Examples

1. 3% of 400

   • Divide 400 by 100: 400/100 = 4
   • Multiply: 3 × 4 = 12
   • Answer: 12

2. 80% of 70

   • Divide by 10 twice:
     • 80/10 = 8
     • 70/10 = 7
   • Multiply: 8 × 7 = 56
   • Answer: 56

3. 24% of 60

   • Divide 60 by 10: 60/10 = 6
   • Divide 24 by 10: 24/10 = 2.4
   • Multiply:
     • 2 × 6 = 12
     • 0.4 × 6 = 2.4
   • Add: 12 + 2.4 = 14.4
   • Answer: 14.4

4. 133% of 1,200

   • Divide 1,200 by 100: 1,200/100 = 12
   • Multiply: 13 × 12 = 156
   • Answer: 156

Conclusion

• Method: Divide by 100 or 10 twice to simplify
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This trick allows for quick percentage calculations without a calculator by simplifying the process through strategic division.