Tech Math Channel: Calculating Percentages Mentally

Introduction

• Presenter: Josh
• Topic: Easiest way to calculate percentages in your head
• Demonstration with examples

Concept of Percentage

• Percentage Definition: "Percent" means per hundred.
  • "Per" = divided by
  • "Cent" = 100 (e.g., 100 cents in a dollar)
• Traditional Method: Percentage calculation by dividing by 100 and multiplying by another number.

Mental Calculation Trick

• Trick: Divide by 100 at any stage, or divide by 10 twice (since 10 * 10 = 100).
• Simplifies mental calculations.

Example 1: 61% of 80

• Simplified Steps:
  1. Divide 80 by 10: 80 / 10 = 8
  2. Divide 61 by 10: 61 / 10 = 6.1
  3. Multiply: 6 * 8 = 48
  4. Add: 0.1 * 8 = 0.8
  5. Result: 48 + 0.8 = 48.8

Additional Examples

Example 2: 3% of 400

• Steps:
  1. Divide 400 by 100: 400 / 100 = 4
  2. Multiply: 3 * 4 = 12
  3. Result: 3% of 400 = 12

Example 3: 80% of 70

• Steps:
  1. Divide 80 by 10: 80 / 10 = 8
  2. Divide 70 by 10: 70 / 10 = 7
  3. Multiply: 8 * 7 = 56
  4. Result: 80% of 70 = 56

Example 4: 24% of 60

• Steps:
  1. Divide 60 by 10: 60 / 10 = 6
  2. Divide 24 by 10: 24 / 10 = 2.4
  3. Multiply: 2 * 6 = 12
  4. Multiply: 0.4 * 6 = 2.4
  5. Add: 12 + 2.4 = 14.4
  6. Result: 24% of 60 = 14.4

Example 5: 13% of 1,200

• Steps:
  1. Divide 1,200 by 100: 1,200 / 100 = 12
  2. Multiply: 13 * 12 = 156
  3. Result: 13% of 1,200 = 156

Conclusion

• Simplify percentage calculations by dividing by 100 or dividing by 10 twice.
• Encouragement to practice and apply the method.
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• Thanks to patrons and viewers.

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