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🧐🤫🤑 When linear equations and geometric progressions are just not doing it for you, it may be time to take a break from math class and impress your friends with a cool calculator trick. All you need is any type of calculator, and you can easily perform some magical math tricks to impress an audience. Don’t forget to put on a dramatic show to enhance the effects!
Method 1Method 1 of 3:Doing the “Number 7” Trick
- 1Tell someone to secretly select a 3-digit number and enter it twice into a calculator. Make sure they do not show you the calculator’s display. Stand across the room from the person and make it seem like you are trying to read their mind.XResearch source
- For example, they could enter "123123."
- 2Announce that the number is divisible by 11 and have them check it. Dramatically announce this from across the room. Have them verify it and then tell the audience that you are right.XResearch source
- For instance, if they entered 123123, then they would divide it by 11 and get 11,193.
- 3Tell them to divide that result by 13. Announce from across the room that the result is divisible by 13. Tell them to do it on the calculator to prove it.XResearch source
- For example, if their last result was 11,193, then they would divide it by 13 and get 861.
- 4Tell them to divide the result by the original 3-digit number. Remember that they chose a 3-digit number and entered it twice. Make sure they only divide the result by 3-digits, rather than the 6 they entered at the beginning.XResearch source
- For instance, if their last result was 861, and the original number was 123, they would divide 861 by 123 to get the number 7.
- 5Announce that the final answer is 7. Tell them without looking at the screen. Have them show the audience, if you have one, to prove that you are right.XResearch source
- You can switch this trick up by having them divide the result by 7 in step 3, and announce that the result is 13 in the final step.
🧐🤫🤑 Tip: You can add a special magic touch to this trick by saying you are going to predict if the person will have good or bad luck. Divide the result by 13 in step 3 to get the result of 7 and predict good luck, or divide the result by 7 in step 3 to get the final number of 13 and predict that they are going to have bad luck.
Method 2Method 2 of 3:Performing the “Secret of 73” Magic Trick
- 1Write "73" on a piece of paper, fold it, and give it to a friend or volunteer. Don't let anyone see the number your write down. You'll reveal this secret number at the end of the trick, to your audience's delight.XResearch source
🧐🤫🤑 Tip: It doesn’t matter what kind of paper you use. Just make sure you fold it up enough that nobody can see the number.
- 2Tell your volunteer to pick a 4-digit number and put it into the calculator twice. Any 4-digit number will work for this trick. Hand the calculator to the volunteer and have them enter the number.XResearch source
- For instance, if your volunteer picks the number "7893," they would type "78937893" into the calculator.
- 3Announce that the number is evenly divisible by 137. Have your volunteer verify this by dividing the 8-digit number in the calculator by 137. Any number made by repeating a 4-digit number twice will be evenly divisible by 137.XResearch source
- For example, 78,937,893 divided by 137 is 576,189.
🧐🤫🤑 Tip: This works because repeating the digits in a 4-digit number twice is equal to multiplying the original 4-digit number by 10,001, which is divisible by 137. Try it!
- 4Tell your volunteer to divide the answer by the original 4-digit number. Your volunteer will get an answer of 73 every time if you've followed the directions right. It doesn’t matter which number they started with.XResearch source
- For instance, after dividing 78,937,893 by 137 to get 576,189, the volunteer would divide 576,189 by 7,893.
🧐🤫🤑 Tip: This works because 10,001 is equal to 137 x 73. Dividing your 8-digit number by 137 gets you an answer that is equal to your original 4-digit number x 73. So, by dividing by your 4-digit number, you'll get 73 as an answer every time.
- 5Command your volunteer to reveal your prediction. Have your friend or volunteer open the folded piece of paper. Be prepared for your audience to go wild when your prediction of 73 is revealed!XResearch source
- Don't reveal the math behind the trick! A good magician knows how to keep their secrets.
Method 3Method 3 of 3:Reading Someone’s Mind
- 1Tell someone to pick a number from 1-9 without telling you. Explain to them that you are going to tell them what number they chose at the end. Put on an act that you are reading their mind while they are thinking of a number.XResearch source
- This is a super easy math trick that is easy to figure out at the end, but it’s still fun to put on a show!
- 2Have them multiply their number on a calculator by "9," then by "12345679." Notice that there is no "8" in the second sequence of numbers. Make sure they multiply the number they chose by "9", then by "12345679," with no "8" in order for the trick to work.XResearch source
- Keep pretending you are reading the person’s mind while they perform the multiplication.
- 3Make them show you the results or pass you the calculator. Tell them you will divide what number they chose at the beginning from the result on the calculator. Have them hold the calculator to face you so you can see the number or hand it to you so you can look.XResearch source
- If you have an audience, don’t let them see the result on the screen in order to create a more dramatic effect.
🧐🤫🤑 Tip: To try to keep your secret, you could have the person hit enter or the equals sign and pass you the calculator right away without letting them looking at the result on the screen.
- 4Look at the number to determine what their original number was and tell them. Whatever number you see repeating on the screen is the number they chose at the beginning. There will only be a string of a single repeating number.XResearch source
- For example, if they chose "1," then the calculator will show "111111111."
- QuestionI tried the Number 7 trick, but the answer is always 1,001. Am I doing things right?Community AnswerYou and they have to go through the whole process of dividing their first repeating number by each step, like this: 123123 ÷ 11 = 11,193; then 11,193 ÷ 13 = 861; and finally 861 ÷ 123 = 7.
- QuestionHow can I type "she" in a calculator?Community Answer345 is "she." Check out the article on How to Write Words With a Calculator for more tips.
- QuestionWhat is the use of CE in pocket calculators?Community AnswerCE is clear error - you use it to clear any erroneous computations, such as dividing by zero.
- QuestionI want to try some tricks involving a calculator and lots of people. How can I do it?Community AnswerHere's what you do. First, get a graphing calculator. Ask for one number from each of the people, and plug it in. Then, tell the audience that you can calculate any number they make into a whole number. Divide by Zero. Bow as the audience applauds!
- QuestionHow can I use a scientific calculator for a trick?Community AnswerIt probably won't work very well for writing words, but will work great for math tricks or puzzles.
- QuestionHow do I make a C on the calculator?Community AnswerOn a scientific calculator, use the bracket on the left. It works sometimes but not always; sometimes it doesn't make the word look right.
About This Article
To do a cool calculator trick, start by writing the number 73 on a piece of paper and folding the paper in half. Hand the paper to a volunteer, but don't let them look at what's on it! Then, ask your volunteer to enter a 4-digit number into a calculator twice so there's an 8-digit number on the screen. When they're finished, ask them to divide the 8-digit number by 137 on the calculator. Now, ask them to divide that number by the original 4-digit number they entered. If they followed your instructions, the final number on the calculator should be 73, regardless of the number they entered at the beginning. Tell them to look at the number on the sheet of paper they're holding. They'll be amazed that you predicted the right number! To learn how to read someone's mind using a calculator, keep reading!