Trick 1: The 11 Times Rule
How It Works• Step 1: Take any two-digit number, for example, 34.
• Step 2: Split the digits: 3 and 4.
• Step 3: Add the digits together: 3 + 4 = 7.
• Step 4: Place the sum between the original digits: 374.
Special Case
• If the sum is 10 or more, carry over:
⚬ Example: 57
⚬ Split digits: 5 and 7.
⚬ Add the digits together: 5 + 7 = 12.
⚬ Place the 2 between the digits and add 1 to the first digit: 627.
Trick 2: Multiplying by 9
To multiply any number by 9 using your fingers, follow these steps:1. Hold out both hands with fingers spread out.
2. For the number you want to multiply by 9, put down the corresponding finger. For example, if multiplying 3 by 9, put down the third finger.
3. Count the fingers to the left of the folded finger for the tens place.
4. Count the fingers to the right of the folded finger for the units place.
This trick works because the sum of the digits in the result of multiplying by 9 always equals 9.
Trick 3: The Finger Multiplication for 9
This trick allows you to multiply numbers 6 through 10 by 9 using your fingers. It's a fun and simple way to do multiplication without needing a calculator or paper.How to Use the Trick
1. Hold both hands in front of you with fingers spread.
2. Assign each finger a number from 1 to 10, starting from the left thumb.
3. To multiply a number by 9, fold down the finger corresponding to that number.
4. Count the number of fingers to the left of the folded finger for the tens place.
5. Count the number of fingers to the right of the folded finger for the units place.
6. Combine these two numbers to get the result.
Trick 4: The Square of Numbers Ending in 5
To easily square any number ending in 5, follow these steps:1. Identify the number: Let's take 25 as an example.
2. Separate the last digit: The number is 25, so focus on the first digit, which is 2.
3. Multiply the first digit by itself plus one: Multiply 2 by (2 + 1), which equals 6.
4. Append 25 to the result: The final result is 625.
This method works for any number ending in 5!
Trick 5: The Magic Number 1089
Steps to Perform the Trick1. Choose a Number: Start with any three-digit number where the digits are in descending order (e.g., 732).
2. Reverse and Subtract: Reverse the digits of your chosen number and subtract the smaller number from the larger one (e.g., 732 - 237 = 495).
3. Reverse and Add: Reverse the result and add it to the original result (e.g., 495 + 594 = 1089). No matter the starting number, you will always end up with 1089!
Why It Works
This trick works due to the properties of numbers and the way place values interact when reversed and manipulated. It's a simple yet fascinating demonstration of mathematical symmetry.