Tricks
Finger Math
Multiplying by 9
Hold out your hands in front of you so that your thumbs point toward one another.
Visualize that your left pinky finger represents 1, the next finger 2, and so on left to right, until your right pinky finger represents 10. Those fingers represent the number you wish to multiply by 9. To do so, simply put the finger down you wish to multiply by 9. All fingers to the left of the down finger represent the tens digit of the answer while all fingers to the right represent the ones digit.
Example: 6 x 9. Put the finger representing 6 down (the right hand thumb). To the left of the down finger, you have 5 fingers up. That's your tens digit. 5. To the right, you have 4 fingers up. There's your ones digit. 4. Put those together and you have your answer: 54.
Rapidly Adding Numbers
Edward Julius in his book Rapid Math Tricks And Tips explains how to add numbers faster.
Here is how to rapidly add numbers.
1+9+2+8+4+5+6+5+3+7=
1+9=10 2+8=10 4+6=10 5+5=10 3+7=10
Think 10, 10, 10, 10, and 10
The answer is 50
Here is another example
3+8+7+1+1+4+5+6+2=
3+8=11
7+1+1=9+11=20
4+6=10
20+10=30
5 and 2 are left so add 5+2 and get 7 and add that to the 30
Your answer is 37
Click here to try some addition games.
Fibonacci Addition Trick
Step 1 Choose two numbers
Step 2 Form a Fibonacci sequence for ten numbers
Example, I choose number 5 for my first number and 6 for my second number.
Then I add the numbers to get a Fibonacci sequence. 5+6 gives my 3rd number which is 11; 6+11 gives me my 4th number which is 17. The entire sequence is as follows:
1st - 5
2nd - 6
3rd - 11
4th - 17
5th - 28
6th - 45
7th - 73
8th - 118
9th - 191
10th - 309
The trick is to multiply the 7th number by 11 (you always multiply it by 11). The answer you get when you multiply the 7thnumber by 11 will always be the same result as if you had added all ten numbers. In the above example, the 7th number is 73. Multiply 73 by 11 and the answer is 803. If you add all 10 numbers together the answer will also be 803.
Try this with your own numbers.
Here are some other useful ways of remembering some mathmaticial operations.
Perimeter: the word rim will help you remember that perimeter measures the distance around the rim of an object.
The number of teaspoons in a tablespoon: There are 3 teaspoons in 1 tablespoon. Remember that both teaspoon and tablespoon start with the letter "t" and the word three rhymes with t.
The order of operations in long division: Remember the phrase "Did my sister bring rabbits?"
| Did | Divide |
| My | Multiply |
| Sister | Subtract |
| Bring | Bring Down |
| Rabbits | Remainder |
A way to remember the order of mathematical operations is to remember the following phrase "Please Exercise My Dear Alligator Sal."
Please Parentheses Exercise Exponents My Multiplication Dear Division Alligator Addition Sal Subtraction