10 Math Tricks That Will Blow Your Mind
Here are 10math tricks that will amaze your friends and maybe even yourself:
1.Multiplying by 6:
- Trick: If you multiply 6 by an even number, the answer will end with the same digit. The numberin the tens place will be half of the number in the ones place.
- Example: 6 x 4 = 24 (The onesdigit is 4, and half of 4 is 2, which is the tens digit).
2. The Answer is Always 2:
- Trick: Think of a number. Multiply it by 3. Add6. Divide this number by 3. Subtract the number from Step 1 from the answer in Step 4. The answer is always 2.
- Explanation: The trick cancels out the original number and leaves you with6 divided by 3, which is 2.
3. Same Three-Digit Number:
- Trick: Think of any three-digit number where all the digits are the same (e.g., 333, 666). Add up the digits. Divide the three-digit number by the sum. The answer is always 37.
- Explanation: The sum of the digits will always be 3 times the digit. The three-digit number is a multiple of that digit and 111. The division effectively cancels out the digit and leaves you with 111 divided by 3, which is 37.
4. Six Digits Become Three:
- Trick: Take any three-digit number and write it twice to make a six-digit number (e.g., 371371). Divide this number by 7, then by 11, and then by 13. The answer is the original three-digit number.
- Explanation: This works because 7 x 11 x 13 = 1001. Dividing by 1001 effectively removes the repeating three-digitsequence.
5. The 11 Rule:
- Trick: To multiply a two-digit number by 11, separate the digits in your mind. Add the two digits together. Place the sum between the two digits. If the sum is greater than 9, carry over the tens digit.
- Example: 72 x 11 = 7 (7 + 2) 2 = 792.
6. Squaring Numbers Ending in 5:
- Trick: To square a number ending in 5, multiply the tens digit by the next highernumber, and then write 25 after the result.
- Example: 25² = (2 x 3) 25 = 625.
7. Multiplying by 9:
- Trick: To multiply a number by 9, multiply it by10 and then subtract the original number.
- Example: 7 x 9 = (7 x 10) – 7 = 70 – 7 = 63.
8. Dividing by 5:
- Trick: To divide a number by 5, double the number and then divide by 10.
- Example: 40 ÷ 5 = (40 x 2) ÷ 10 = 80 ÷ 10 = 8.
9. Finding the Percentage:
- Trick: To find 10% of a number, move the decimal point one place to the left. To find other percentages, use this as a base.
- Example: 10% of 200 is 20. To find 20%, double the result (40).
10.The Casting Out Nines Trick:
- Trick: To check if a multiplication or addition problem is correct, sum the digits of each number until you get a single digit. Do the same for the result. If the sum of the digits of the result matches the sum of the digits of the original numbers, the calculation is likely correct.
- Example: 123 + 456 = 579. Summing the digits: 1+2+3 = 6, 4+5+6 = 15 (1+5=6), 5+7+9 = 21 (2+1=3). The sums don’t match, so the calculation is incorrect.
These tricks are fun and useful for quick calculations, but remember that understanding the underlying math concepts is crucial for true mathematical proficiency.
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