Fast Math Tricks - How to multiply 2 digit numbers up to 100 - the fast way!

tecmath
26 Nov 201106:26
EducationalLearning
32 Likes 10 Comments

TLDRIn this engaging video from the TecMath channel, the host introduces a quick method for multiplying two-digit numbers without the need for a calculator. The video begins with a challenge for viewers to multiply 21 by 31, offering a six-second countdown. After revealing the correct answer, the host proceeds to explain a step-by-step process that involves multiplying the first and last digits of the numbers, and then a clever trick for finding the middle digits by adding the products of the other pairs of digits. The video continues with additional examples, such as multiplying 43 by 21 and 42 by 63, demonstrating the method's effectiveness and ease. The host encourages viewers to practice the technique to impress their teachers and peers, and assures them that making mistakes is a natural part of learning. The video concludes with a set of practice problems for viewers to solve, followed by the solutions, reinforcing the method's practicality and encouraging further practice.

Takeaways
  • ๐Ÿ“š Start with a basic multiplication question: Multiplying 21 by 31 to introduce the method.
  • โณ Give viewers a short time frame to solve the problem, encouraging quick thinking.
  • ๐ŸŽ‰ Congratulate those who get the correct answer without a calculator, emphasizing the goal of mental math.
  • ๐Ÿ”ข Show the step-by-step process for multiplying two-digit numbers without a calculator.
  • ๐Ÿ“ Explain the multiplication method: Multiply the first digits, leave a space, multiply the last digits, and then multiply the outer and inner digits, adding them together.
  • ๐Ÿ’ก Highlight a trick for handling the middle part of the multiplication, especially when carrying over numbers.
  • ๐Ÿšซ Emphasize that a calculator is not needed for such calculations once the method is mastered.
  • ๐Ÿค“ Encourage practice to become proficient and impress others with mental calculation skills.
  • ๐Ÿ˜… Acknowledge that mistakes can happen, even to the presenter, and it's part of the learning process.
  • ๐ŸŒˆ Use different colors to keep the presentation engaging and to avoid confusion.
  • ๐Ÿ“ˆ Provide additional practice problems for viewers to test their understanding and newly learned skills.
  • ๐Ÿ‘ End with a positive note, encouraging viewers to continue practicing and to not be discouraged by initial difficulties.
Q & A

  • What is the main topic of the video?

    -The main topic of the video is a fast method for multiplying two-digit numbers without using a calculator.

  • How much time is given to the audience to solve the first multiplication problem?

    -The audience is given six seconds to solve the first multiplication problem.

  • What is the correct answer to the multiplication of twenty-one and thirty-one?

    -The correct answer to the multiplication of twenty-one and thirty-one is 651.

  • How does the video demonstrate the multiplication of the first digits of the two numbers?

    -The video demonstrates multiplying the first digits (2 x 3) to get the first part of the answer, which is 6.

  • What is the trick used to find the middle part of the product when multiplying two-digit numbers?

    -The trick involves multiplying the first digit of the first number by the second digit of the second number and the second digit of the first number by the first digit of the second number, then adding these two products together.

  • What is the result of the multiplication of 43 and 21?

    -The result of the multiplication of 43 and 21 is 903.

  • How does the video handle the situation when the middle part of the product has more than one digit?

    -When the middle part of the product has more than one digit, the video demonstrates carrying over the tens digit to the next place value and adding it to the next digit in the multiplication process.

  • What is the final multiplication problem presented in the video?

    -The final multiplication problem presented in the video is 42 times 63.

  • What is the result of the multiplication of 42 and 63?

    -The result of the multiplication of 42 and 63 is 2646.

  • What advice does the presenter give to the audience regarding making mistakes?

    -The presenter advises that everyone makes mistakes and that it's okay to make a few while practicing the multiplication technique.

  • What is the presenter's final message to the audience?

    -The presenter's final message is to practice the multiplication technique, as it will impress others and make them think the audience members are geniuses.

  • What are the three additional multiplication problems provided at the end of the video for the audience to practice?

    -The three additional multiplication problems are: 22 times 32, 51 times 63, and 82 times 51.

Outlines
00:00
๐Ÿค“ Introduction to Quick Multiplication Techniques

The video begins with a warm welcome and an introduction to a fast method for multiplying two-digit numbers. The host challenges viewers to calculate the product of 21 and 31 within six seconds, revealing that the correct answer is 651. The host then proceeds to explain a quick way to multiply numbers without a calculator. The method involves multiplying the first and last digits of the numbers to get the first and last parts of the answer, respectively, and then using a trick to find the middle part by multiplying certain digits and adding the results. The process is demonstrated with the example of 21 times 31, followed by another example, 43 times 21, where the host shows how to handle carrying over digits when the multiplication results in a two-digit number. The host emphasizes that practice will lead to proficiency and impresses upon viewers the importance of not relying on calculators for such calculations.

05:00
๐Ÿ“š Demonstrating Multiplication with Additional Examples

The host continues the lesson with more examples to solidify the multiplication technique. The next problem presented is 42 times 63, and the host makes a mistake, humorously acknowledging the need to remake the video due to the error. The correct process is then shown, with the host multiplying the first digits to get the first part of the answer, and the last digits for the final part, then adding the products of the inner digits to form the middle part of the answer. The host successfully calculates the product as 2464. The video concludes with a few more practice problems for the viewers to solve: 22 times 32, 51 times 63, and 82 times 51. After a pause for viewers to attempt the problems, the host provides the solutions: 704, 3213, and 4182, respectively. The host encourages viewers to keep practicing these techniques to become adept at mental arithmetic and impress others with their skills.

Mindmap
Keywords
๐Ÿ’กMultiplication
Multiplication is a mathematical operation that involves combining a certain number of groups of equal size. In the video, it is the core operation being taught, specifically for two-digit numbers. The video aims to help viewers master a quick method for multiplying two-digit numbers without the need for a calculator, which is central to the educational theme of the video.
๐Ÿ’กTwo-digit numbers
Two-digit numbers refer to integers that have two digits, such as 10 to 99. The video focuses on multiplying these types of numbers using a fast method. This concept is fundamental to the video's content, as it is the specific type of numbers being multiplied to demonstrate the quick multiplication technique.
๐Ÿ’กQuick method
The quick method refers to a technique or strategy that allows for a faster way to perform a task, in this case, multiplication. The video teaches viewers how to multiply two-digit numbers quickly by breaking down the process into simpler steps, which is the main instructional focus of the video.
๐Ÿ’กFirst digits
First digits are the tens place numbers in a two-digit number. In the multiplication technique explained, the first step involves multiplying the first digits of the two numbers to get the first part of the answer. For example, in multiplying 21 by 31, the first step is to multiply 2 (the first digit of 21) by 3 (the first digit of 31), resulting in 6.
๐Ÿ’กLast digits
Last digits refer to the ones place numbers in a two-digit number. In the quick multiplication method, after multiplying the first digits, the last digits of the two numbers are multiplied to get the last part of the answer. This step is demonstrated when the video shows multiplying the ones digit of 21 (which is 1) by the ones digit of 31 (also 1), resulting in 1.
๐Ÿ’กMiddle part
The middle part of the product in the quick multiplication method is obtained by multiplying the first digit of one number with the last digit of the other number and vice versa, then adding these two products together. This step is crucial for getting the correct product and is demonstrated in the video when multiplying the numbers 43 and 21, resulting in the middle part being calculated as (1*4) + (3*2) = 10.
๐Ÿ’กCarry over
Carry over is a concept used in arithmetic when a digit is added to another digit resulting in a sum that is 10 or more, and the excess is 'carried over' to the next higher place value. In the video, when the middle part of the multiplication results in a two-digit number, the carry over is used to adjust the final answer. For example, when multiplying 43 by 21, the carry over from the middle part (10) is added to the first part (8), resulting in 90 as the middle part of the final answer.
๐Ÿ’กPractice
Practice is the act of repeatedly doing something to improve one's skill or knowledge. The video encourages viewers to practice the quick multiplication method to become proficient and fast at it. Practice is emphasized as a key component of mastering the technique and impressing others with one's arithmetic skills.
๐Ÿ’กCalculator
A calculator is an electronic device used to perform arithmetic operations. The video mentions calculators to contrast the quick multiplication method with the traditional reliance on calculators, suggesting that viewers can achieve the same results without one. The mention of calculators serves to highlight the efficiency and practicality of the method being taught.
๐Ÿ’กGenius
A genius is a person with exceptional intellectual or creative power. In the video, the term is used humorously to suggest that mastering the quick multiplication method can make one appear to be a genius, as it allows for impressive mental arithmetic. This term is used to motivate and inspire viewers to learn and practice the method.
๐Ÿ’กMistakes
Mistakes are errors or inaccuracies. The video acknowledges that everyone, including the presenter, can make mistakes. This is used to create a relatable and supportive tone, encouraging viewers not to be discouraged by errors but to learn from them. The concept of making mistakes is important as it humanizes the learning process and emphasizes the importance of perseverance.
Highlights

Introduction to a fast method for multiplying two-digit numbers without a calculator.

Quick multiplication challenge: 21 multiplied by 31 equals 651.

Explanation of the multiplication technique, starting with the first digits and moving to the last.

The trick for finding the middle part of the product by multiplying and adding pairs of digits.

Demonstration of the multiplication method with the example of 43 times 21, resulting in 903.

Addressing a common mistake and how to correct it when the multiplication results in a two-digit number.

Another multiplication example: 42 times 63, showcasing the method's application with different numbers.

Emphasizing the importance of practice to master the multiplication technique.

Encouragement that with practice, one can impress teachers and peers with their multiplication skills.

Acknowledgment of the potential for making mistakes and the importance of learning from them.

Presentation of additional practice problems for viewers to test their new skills.

Working through the solutions for the practice problems, providing a step-by-step guide.

Final multiplication example: 22 times 32, resulting in 704.

Solution to the problem 51 times 63, showing the step-by-step calculation leading to 3213.

Final challenge problem: 82 times 51, with a detailed breakdown of the multiplication process.

Conclusion and a reminder to practice the method to achieve proficiency in mental multiplication.

The presenter's light-hearted approach to making a mistake and the importance of learning from it.

The presenter's use of different colors to keep the viewer engaged and to differentiate between examples.

Transcripts

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