## How to find the magic number in math

This is an old classic that is based on a quirk in mathematics. It's an easy magic trick that has something of a mentalism effect. In a prediction effect, you appear to predict the future. In magic or mentalism, the prediction is typically a parameter——word, number, event, or the result of a random compilation——that spectators have come together to form.

Sometimes, the prediction is something that only a spectator might know. In this routine, which is a mathematical-based prediction, a series of seemingly random mathematical processes are applied to a freely named number, and the magician proves to have known in advance the final result. Write "Elephants in Denmark" on a piece of paper. Fold this up and keep it with you. Next, read the following to your spectator or audience, giving them time to make the necessary calculations:.

For fun, you can carry pictures that suggest elephants in Denmark. This way, instead of simply writing down "elephants in Denmark," you can show a picture that will create a stronger impact.

You can also perform this as a mind-reading stunt. At the end of the instructions, you ask the spectator to think about the final image and then you tell him.

The sequence presented in this trick is seemingly random and combines elements of math, the alphabet, and freely named elements suggested by the results of prior steps.

When you study the steps, you'll find that the mathematical procedure will always result in the same number, four. This is because any single-digit number multiplied by nine will result in a special two-digit number. Add the individual digits of these two-digit numbers together and you'll always get nine.

And, of course, when you subtract five from nine, you'll arrive at four. That said, should the wrong country be named, the jig is up.

As a last resort and saving grace, you can state that you knew that the letter would be D. Ask anyone to name an animal that starts with the letter E and an elephant is sure to be the first that comes to mind. Since this is so obvious, some may try to think of something more obscure such an eel, but should this happen, at least you can show that you were able to predict Denmark and that the second letter was E.

Pick a number between two and nine. It can be two or it can be nine, or any number in between. Take the number that you've chosen and multiply it by nine. This should give you a two-digit number. Take the two digits of the number and add them together. For example, if your number is 16, take the one and six and add them to make seven. Take the resulting number and subtract five from it.

Take that number and correspond it to a letter in the alphabet. ### Easy Magic Trick: The Mental Prediction

Home Questions Tags Users Unanswered. Explain the Magic Numbers! Ask Question. Asked 5 years, 5 months ago. Active 2 years, 11 months ago.

### Analyzing Existing Subnets - Faster Magic Number Method

Viewed 12k times. Trick 1 Think of a number between 1 and 9 Multiply by 9 Add up all of the digits of this number Divide by 3 Subtract 2 Your answer? Trick 2 Think of any positive number!

Double it. Add 2. Half it. Add 3. Subtract your original number. Your answer is obvious, it's 4 Trick 3 Pick any positive 3 digit number in the universe. Multiply by 7. Multiply by Your answer is your original number twice :O Trick 4 Think of a number between 1 and 9. Add 5. Multiply by 5. Add another digit between 1 and 9 to it.

Subtract The first digit of your new number was your original number. The second is your second number. Active Oldest Votes. It's actually always 4. The numbers are actually 7, 11, and 13, because multiplying these is A three digit number times is the same as taking the number with 3 0's after, then add the number.

I meant 11 after I took out my calculator, but I must have forgotten to fix.Have you ever noticed that the number 9 is kind of amazing? What's that…did I hear you say "NO? After our 3 frequently asked questions about math puzzles episode last week, math fan Cynthia wrote to tell me about one of her favorite puzzles.

As luck would have it, Cynthia's puzzle is based upon one of the same ideas that—as we'll soon find out—makes our as-yet-unexplained third-and-final puzzle from last time tick. What's the tie-in between the two? As we'll see, they're both based upon some pretty amazing properties of the mysterious and sometimes seemingly magical number 9.

How does it all work? And what makes the number 9 so "magical? This is definitely one that you'll want to play along with. Here's how it goes: Start by thinking of a number, any number. Now, multiply that number by 9. If that new number is still a multi-digit number, add its digits together to come up with yet another new number.

Continue doing this until you end up with a 1-digit number. Once you have a 1-digit number, subtract 5 from it. Now, using the standard numbering of the English alphabet where 1 is A, 2 is B, and so onfind the letter corresponding to your number.

Next, think of a European country that begins with that letter. Then take the last letter of that country and think of an animal that begins with that letter. Finally, take the last letter of that animal and think of a color that begins with that letter. Okay, now—oh, wait a minute—you do know that there aren't any orange kangaroos in Denmark, right?

Is that what you came up with? If not, you're probably thinking I'm crazy right now. But I'm betting that "orange, kangaroos, and Denmark" are exactly what a bunch of you did come up with.Lay off of the morning math worksheets and try out some of these magical math puzzles that show students how math can be enchanting!

Calendar Magic 9 Impress your friends with this math multiplication magic trick from Murderous Maths! Kids tell a friend to put a square around 9 numbers on a calendar 3 x 3 box. Then, they say they can find the sum of the 9 numbers within the square in a flash! Abracadabra and alakazam! All they do is multiply the number in the center of the square by 9 and presto! They magically have the answer! Magic Square A Magic Square is a great tactile, thinking game for kids, that has them rearrange three numerals horizontal, vertical, and diagonal so they all equal one sum, a magical number!

Kids love the use of milk caps because they can slide and glide them around on a flat table top. Magic Squares are also a good way for kids to improve their addition skills using a group of addends, three whole numbers in an equation.

All you need are 6 milk caps labeled Kids slide the milk caps around, forming a triangle. Their goal is to have all 3 sides add up to equal the same sum.

Toothpick Math Puzzles Geometric toothpick puzzles that help develop problem solving and critical thinking skills. Art in Numbers Practice your multiplication tables by creating grid paper designs from Sharynideas! Kids identify patterns in their multiplication tables. When they identify a repeating pattern, they create art! Check out the activity here!

Also, visit NRich Math for a slightly different way to create designs from your times tables! Walk Through Paper Can you walk through a hole in an 8. Pass out a sheet of paper to all of your students and see if they can figure out how to cut a hole large enough for them to fit through. Then, show them this magical trick! Afterwards, stretch your paper out and try to find the area and perimeter of your paper! How did it change? For younger students, this project can tie into a basic measuring unit.

You can even fit through an index card! Click here for details! All they need is a set of dominoes! Click here for the full list! Check out domino magic squares and rectangles here! Then, they just subtract corner to corner. The big surprise is their final square!

Like magic, all of the corners are the exact same numeral! Inference : See if kids can predict what will be their mystifying number before solving all their squares! Think of a whole number 1 through 10 2. Double it!A combination mechanism for a safe comprises thirty-two tumblers numbered from one to thirty-two in such a way that the numbers in each wheel total Could you open the safe?

But the really clever trick is explaining to them why these 'tricks' are maths and not magic. Like all good magicians, you should practise by trying them. Can you explain how they work? Try this with a different starting number. Did you get a different result? Why does this happen? Write the answer on a piece of paper without letting anybody see it and seal it in an envelope. Have somebody hold the envelope and at the end ask them to open it and reveal the number you wrote at the beginning.

Wow, Magic! Without giving you any information, ask a friend to count the value of some coins and write the amount on a piece of paper.

Then ask your friend to:. For the grand finale, you ask for the final answer. Take off the last digit and you will be able to work out how much the coins are worth! Look at the answer, the hundreds are the age and the remaining digits are the shoe size.

If for instance somebody shows youthere are 11 hundreds - the age, and the remaining digits 05 or 5 show the shoe size. Now, how on earth does that work? Main menu Search. Hide Menu. Problem Solution You may also like Calendar Capers Choose any three by three square of dates on a calendar pageSkip to content.

## Maths and magic

By Michael Hartley A magic square is a grid containing the numbers 1, 2, 3, and so on, where each row, column and diagonal add up to the same number. An example is shown below, you will see that each row, column and diagonal add up to This number 34 is the " magic number " of the magic square. Finding magic squares or solving magic square puzzles is much easier if you know the magic number. The good news is, once you know the size of the magic square you want, you can calculate the magic number without too much trouble.

This is because of an amazing fact : The magic number depends only on the size of the square grid, not on how the numbers are arranged within it Why is this? Suppose you add up each row of a magic square. Each row will add up to the magic number. So if you add all the cells together, you have added up this magic number as many times as there are rows in the grid. Let's note this fact: The sum of all the cells in the grid is the magic number times the number of rows But there's another way to add all the cells together, since each number 1, 2, 3 and so on appears exactly once.

The biggest number in the grid is the number of rows times the number of columns. Therefore, The sum of all the cells in the grid is the sum of all the numbers from 1 up to the number of rows times the number of columns.

A magic square has the same number of rows as columns, so the magic number depends only on the number of rows in the magic square. The following steps help you work it out : Take the number of rows, and multiply this by itself Add one multiply again by the number of rows.

To save you some calculations, I've given below the magic numbers of a few different sizes of magic square : for a 3 by 3 square, the magic number is Yours, Dr Mike!

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Math magic tricks can liven up any math class and create a sense of wonder and curiosity about math. Not only that, math magic creates a new context for algebraic reasoning as students go beyond "What's the answer?

## An Introduction to Magic Squares

One type of number trick involves adding, subtracting, multiplying, or dividing by a starting number and subtracting the original number in such a way that each participant always arrives at a certain number:. Think of a number between 1 and Double your number. Add Multiply this number by 3. Divide this number by 6. Subtract your original number. Now your number is 13! Write a three-digit number. The first and last digits should have a difference of more than one. Reverse the digits and write down this new number.

Subtract the smaller number from the larger one. Circle your answer. Reverse the digits and add this new number to the circled number. Your number is ! Write the year of your birth. Double it. Add 5. Multiply by Add your age. Subtract The first four digits are the year of your birth. The last two digits are your age. The resources at the end of this article encompass a variety of math magic ideas presented in kid-friendly fashion. Adapt number tricks for younger students by asking them to choose a starting number less than 20 or even less than After enjoying a math magic show, guide students in understanding how one of the tricks works.

Challenge older or advanced students to figure out on their own how a trick works and then explain it so everyone else can understand. Students could work in small groups to explain a trick quickly and effectively. Many math magic tricks call on students to compute with the four basic operations -- sometimes applied to very large numbers. In the context of math magic, computational practice is fun.