How to Calculate Faster than a Calculator - Mental Math #1

Key Concepts

Mental Math, Two-Digit Multiplication, Three-Digit Multiplication, Multiplication by 11, Same First Digit Multiplication, Ending in Five Multiplication, Sum of Ending Digits is 10 Multiplication, Speed Calculation.

Multiplying Two-Digit Numbers by 11

• Method: Write the two digits of the number with a space in between. In the space, write the sum of the two digits.
  • Example: 43 * 11. Write 4 and 3. 4 + 3 = 7. Answer: 473.
• Carry-Over: If the sum of the two digits is greater than or equal to 10, carry the one to the first digit.
  • Example: 68 * 11. Write 6 and 8. 6 + 8 = 14. Carry the 1 to the 6, making it 7. Answer: 748.

Multiplying Three-Digit Numbers by 11

• Method: Write the first and last digits of the number with spaces in between. In the first space, write the sum of the first two digits. In the second space, write the sum of the last two digits.
  • Example: 352 * 11. Write 3 and 2. 3 + 5 = 8. 5 + 2 = 7. Answer: 3872.
• Carry-Over: If any sum is greater than 9, carry the one to the next digit.
  • Example: 574 * 11. Write 5 and 4. 5 + 7 = 12. 7 + 4 = 11. Carry the 1 to the 5, making it 6. Carry the 1 to the 2, making it 3. Answer: 6314.

Multiplying Two Two-Digit Numbers with the Same First Digit and Ending in Five

• Method: Multiply the first digit by the next higher digit. Add 25 to the result.
  • Example: 75 * 75. 7 * 8 = 56. Add 25. Answer: 5625.
  • Example: 35 * 35. 3 * 4 = 12. Add 25. Answer: 1225.

Multiplying Two Two-Digit Numbers with the Same First Digit and Sum of Ending Digits is 10

• Method: Multiply the first digit by the next higher digit. Multiply the two last digits. Combine the results.
  • Example: 44 * 46. 4 * 5 = 20. 4 * 6 = 24. Answer: 2024.
  • Example: 67 * 63. 6 * 7 = 42. 7 * 3 = 21. Answer: 4221.

Conclusion

The video presents several mental math tricks to perform calculations faster than a calculator. These tricks focus on specific types of multiplication problems, such as multiplying by 11, multiplying numbers with the same first digit and ending in 5, and multiplying numbers with the same first digit and ending digits that sum to 10. The video emphasizes that practice is key to mastering these techniques and achieving lightning-fast calculation speeds. The presenter encourages viewers to practice the tricks and promises a part two with more interesting tricks if the video receives 10,000 likes.