Summary
In today's lecture on TechMath, led by Josh, we explored a quick mental math multiplication technique for numbers that begin with the same tens digit. By the end of this guide, you should be able to perform such multiplications in under 4 seconds, enhancing your mental calculation speed and effectiveness.
Key Points of the Multiplication Trick
1. Identifying Appropriate Numbers
- The trick applies exclusively to pairs of numbers that start with the same tens digit.
2. Steps to Perform the Trick
- Add the Units: For two numbers, add the unit of one number to the entire other number, or vice versa.
- Example with 23 and 24: Either add 3 to 24 or 4 to 23.
- Result: 27
- Multiply by the Tens Digit: Multiply the result from step 1 by the tens base digit.
- Example with 23 and 24: Multiply 27 by 2.
- Result: 54
- Multiply Units, Then Add: Multiply the units of the two original numbers and add this to the product of step 2 after multiplying it by 10.
- Example: (54 * 10) + (3 * 4) = 540 + 12 = 552
3. Additional Examples
- 33 multiplied by 39:
- (33 + 9) * 3 = 126; 126 * 10 + (3 * 9) = 1260 + 27 = 1287
- 74 multiplied by 78:
- (74 + 8) * 7 = 574; 5740 + (4 * 8) = 5740 + 32 = 5772
- 58 multiplied by 52:
- (58 + 2) * 5 = 300; 3000 + (8 * 2) = 3000 + 16 = 3016
- 108 multiplied by 112 (different tens digits, adjusted strategy):
- (108 + 12) * 10 = 1200; 12000 + (8 * 12) = 12000 + 96 = 12096*
4. Utilization of the Trick
- This trick is notably helpful for rapid mental calculations, which is particularly useful in exams or day-to-day quick math requirements.
- By mastering these steps, you can enhance your mental arithmetic capabilities significantly.
Additional Resources
- Josh mentioned that this video is part of a series, with a playlist available in the video description for further learning.
Feedback and Practice
- Viewers are encouraged to practice these examples and comment on their progress or difficulties, fostering an interactive learning environment.
Feel encouraged to practice this technique with various examples to become proficient and improve your mental arithmetic speed considerably.