*(at least four digits long). e.g. 78341**Ask the friend to add up the digits...e.g. 7+8Even tho+3+4+1=23*

*and then subtract the answer from the first number. e.g. 78341-23=78318*

*Your friend then crosses out ONE digit from the answer. (It can be any digit except a zero) e.g. 7*318*

*Your friend then reads out what digits are left . e.g. 7-3-1-8*

*Even though you haven't seen any numbers, you can say what the missing digit is EIGHT!*

__THE SECRET__

This great trick relies on the power of 9. How?After your friend has added up the digits and subtracted them, the answer will ALWAYS divide by 9. If a number divides by nine, then when you add the digits up, they will also divide by 9. If you check our example 7+8+3+1+8=27

When your friend crosses a digit out, he then reads out the digits that are left. you add them up. In the example, we had 7+3+1+8=19

All you do now is see what you have to add on to your answer to get the next number that divides by nine! The next number to divide by 9 after 19 is 27. SO you need to add EIGHT. This is the number that was crossed out!

Here's another example:

Say the number written down is 875625624.

Your friend adds the digits 8+7+5+6+2+5+6+2+4=45

Your friend does the subtraction: 875625624-45=875625579

( So far you have NO IDEA what numbers are whizzing around!)

Your friend crosses a digit out 87562*579 and tells you what's left. You add 8+7+5+6+2+5+7+9=49

The next number that divides by 9 after 49 is 54. As 54-49 =6, this means that 5 is the missing digit!

Stay with us and enjoy the math beauty,