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Missing Number

Without looking at your friend, ask him/her to write down any number that is at least four digits long.
Example :  13579

Then ask your friend to add up the digits.
1+3+5+7+9 = 25

Now subtract this answer (25) from the first number.
13579 - 25 = 13554

Ask your friend to cross out one digit from the answer. (You can not cross out a zero)

Now ask our friend to slowly read out the digits that are left.

You now magically say : "The missing number is three."

How to do the missing number math trick

This is a power of 9 trick.

Once your friend crosses out a digit and reads out the digits that are left,  you simply add them up.
Example : 1+5+5+4 = 15

You now add on to your answer to get the next number that divides by nine!

The next number to divide by 9 after 15 is 18.
Therefore you need to add on three.
This is the number that was crossed out!

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