Magic Number

Knowing mathematics can make you seem to have psychic powers.

1. Mind Reading

Materials Needed

Paper, pen, phone book, envelope.

Before doing this demonstration, you need to write the number 1089 onto a piece of paper. Then put it in the envelope and seal it.

The demonstration is done as follows:

1. Tell the audience some nonsense about you being able to predict the future or read their minds. Give someone the envelope. Ask them not to open it yet.
2. Ask for a three digit number, where all the digits are different. Write it down.
3. Write the number backwards.
4. Subtract the smaller from the larger. You will now have either a two or three digit number. It will have a 9 in the tens column.
5. Write this new number backwards. If it is a two digit number, you need to write a zero at the end. (e.g. 94 goes to 490).
6. Add these two numbers. You will get 1089.
7. Open the envelope to reveal the answer.

2. When Were You Born

With this trick you can tell someone their age the month that they were born in and the day they were born on. 

Now tell your friend to: 

1. Write down the number of the month they were born on.
2. Multiply by 100.
3. Add the day of the month they were born on. 
4. Multiply by 2. 
5. Add 9. 
6. Multiply by 5. 
7. Add 8. 
8. Multiply by 10. 
9. Subtract 419. 
10. Add his age. 
11. Subtract 111.

The 2 digits on the right is the person’s age. The 2 digits on the left from the person’s age is the day that they were born on. The numbers that are left are the month your friend was born in.

Here is an example: Pretend that the person’s age is 16 and was born on November 4th. 

1. He writes down 11 for November. 
2. He multiplies by 100:1100 
3. He adds the day of the month, 4:1104 
4. He multiplies by 2:2208 
5. He adds 9:2217 
6. He multiplies by 5:11085 
7. He adds 8: 11093 
8. He multiplies by 10:110930 
9. He subtracts 419:110511 
10. He adds his age: 110527 
11. Then he subtracts 111 and he gets 1110416.

The 2 numbers on the right tell you he is 16. The middle numbers tells you the day of the month he was born. The first 2 numbers tell you he was born in the 11th month, November

Photo: "Math Homework" by Kolchogo Tiko