If you're tired of linear equations and geometric series, maybe it's time to take a break from complex math calculations, and wow everyone with a cool calculator trick. You just need a calculator (any type) to do some magical math tricks that will amaze a lot of people. Don't forget to add a dramatic atmosphere to add to the effect.
Method 1 of 3: Performing the “Number 7” Trick
Step 1. Ask someone to choose a 3 digit number without calling it, and type the number into the calculator 2 times
Make sure you can't see the calculator screen. Stand some distance away from the person, and make it seem as if you are reading their minds.
For example, he could select the number "123" and type it into the calculator as "123123"
Step 2. Tell him that the number is divisible by 11 (that is, the result is an integer, without the comma), and ask him to check it
Announce this from afar dramatically. Ask him to confirm and tell the audience this that your guess is correct.
For example, if he enters the number 123123 and divides it by 11, he will get the number 11,193
Step 3. Have him divide the result by the number 13
Tell him from afar that the result will be divisible by 13. Ask him to prove it on a calculator.
For example, if the result of his division is 11,193, he must divide this number by 13, which returns 861
Step 4. Ask him to divide the result by the 3 digit number he chose at the start
At the beginning, he was asked to choose a 3 digit number and enter it into the calculator 2 times. Have him divide the result by the 3 digit number instead of the 6 digit entered on the calculator.
For example, if the result of the last division was 861, and the number he chose at the start was 123, then he would have to divide 861 by 123, which would result in the number 7
Step 5. Announce that the answer is 7
Tell this without looking at the screen. Have him show the audience the calculator screen (if any) to prove that you are right.
You can change this trick by having the person divide the final result in step 3 by 7, and announce that the result of the division in the last step is 13
You can add a touch of magic to this trick by telling her that she will have good or bad luck. Divide the result in step 3 with the number 13 to get the number 7, which means good luck, or divide the result in step 3 by 7 to get the number 13, which is an unlucky number for the person.
Method 2 of 3: Performing the “Secret Number 73” Trick
Step 1. Write the number “73” on a piece of paper, then fold it and give the paper to a volunteer or friend
Don't let anyone see the numbers written on the paper. You will reveal this secret number at the end of this magic trick to amaze the audience.
You can use any paper, as long as it can be folded tightly enough so you can't see the numbers.
Step 2. Ask a volunteer to choose a 4-digit number and enter it into the calculator 2 times
He can choose any 4 digit number. Ask a volunteer to enter the 4-digit number into the calculator.
For example, if the volunteer selects the number "7893", he or she must enter it into the calculator twice so that the number will be "78937893"
Step 3. Tell the number that it will be divisible by 137
Have a volunteer prove it by dividing the 8-digit number by 137 using a calculator. Any number created by entering a 4-digit number 2 times must be divisible by 137.
For example, the number 78,937,893 divided by 137 gives 576,189
This trick works because entering a 4-digit number 2 times is the same as multiplying the 4-digit number by 10.001, which is divisible by 137. Try it out!
Step 4. Ask the volunteer to divide the result by the 4 digit number he chose
If the steps are followed correctly, he will get the number 73, regardless of the number he chose at the start.
For example, after dividing the number 78,937,893 by 137 and getting 576,189, the volunteer must divide 576,189 by 7,893 (this is the number he chose himself at the start)
This trick works because 10, 001 is the product of 137 by 73. Dividing an 8-digit number by 137 will give you the same result as multiplying the first 4 digits of the number by 73. So if you divide the result (576,189) by the 4th digit number, selected at the start (7,893), you will always get 73.
Step 5. Ask a volunteer to open the guess you wrote down on the paper
Ask him to unfold the paper on which you have written the predicted numbers. When the number 73 you wrote is shown, the audience will be amazed.
Don't reveal the mathematical formula that underlies this trick. A good magician should be able to keep his secret
Method 3 of 3: Reading Someone's Mind
Step 1. Have someone choose a number between 1 and 9 without mentioning it
Let him know that you will reveal the number he chose at the end. Act as if you're reading his mind while he's thinking about the numbers to pick.
This is a very simple math trick and easy to understand if you know the secret, but fun to show
Step 2. Have him multiply the selected number by "9", then multiply it again by "12345679"
Look carefully, there is no "8" in this second number. Make sure he multiplies the number of his choice by "9", then by "12345679", without the number "8" for this trick to work.
Continue to act as if you're reading his mind when he's doing the multiplication
Step 3. Have him show you the product or give you his calculator
Say that you will divide the number he chose at the beginning of the multiplication result on the calculator. Ask him to hold the calculator so you can see the numbers, or hand the calculator to you so you can see it.
If there is an audience, don't let them see the multiplication result on the calculator screen so that the dramatic effect is more pronounced
To keep it a secret, have the volunteer press enter or "equals" and hand you the calculator right away, without letting them know the result of the multiplication on the calculator screen.
Step 4. Look at the numbers on the screen to determine which number he chose, and say the number
Any number that is repeatedly displayed on the calculator screen is the number that the person selected at the start. There you will only see a row containing the same number repeatedly.