How to Amaze Your Friends With a Simple Math Trick

Math can be fun at times.

Math and fun might not typically be words used in the same sentence, but there are times when a little learning can be a great way to play a trick on friends. To optimize a simple math trick, give your friend a piece of paper and pencil so he can use as big a number as he wants. This makes the trick even more amazing.

Things You'll Need

• Paper
• Pencil or pen

Instructions

1. Tell your friend to think of a number and write it down without letting you see it. It can be as small or as large as he likes. For example, let's say he writes down 16.

2. Tell your friend to double the number. For this example, it would be 16 times 2 equals 32.

3. Tell him to add a certain number to his current number. For example, tell him to add 22 to the number he has. This would yield:

   32 plus 22 equals 54.

4. Tell your friend to divide by 2. For example, 54 divided by 2 equals 27.

5. Tell him to subtract his original number. In this case, it would be 27 minus 16 equals 11.

6. Tell him you know the number: 11. Don't explain that the way you got this number was simply by dividing the only number you supplied -- 22 -- in half. Basically, what you've done is given him a series of steps and then reversed those steps, plus dividing your number by 2.

Tips & Warnings

• Always pick an even number for step 3, so it will be a whole number when you divide it by 2. You can use any number, but make sure you don't use the same number twice with the same friend.

• Don't always pick same number to add because you will always be giving the same answer. If you always pick 10 the answer will always be 5.

References

• Mudd Math Fun Facts: Mind-Reading Number Trick

Resources

• Read this Article in Spanish