Came across a nice little trick I thought I should pass on. Very neat little trick.

You get the participant to choose a random 5 digit number, multiply by 10, subtract the original number and add 234. They will get a 6 digit number. Ask them to hide one digit and tell you the rest of the five digits. I suppose the digits given can be in any order.

If the six digits of the answer are added together, they will give a multiple of nine, so adding the rest of the five and subtracted from the next multiple of nine will give you the digit that they are hiding.

There is just one flaw, if the addition of the five digits given come to a multiple of nine then the answer can be either 0 or 9 as both added to the total of the five digits will give a multiple of nine.

eg.

52378

52378*10= 523780

523780-52378=471402

471402+234= 471636

If say 6 is hidden so add 4+7+1+3+6=21, next multiple up of nine is 27, so 27-21=6, the number hidden is thus six

Hope you like it, have fun!

The Spray Can