Strike rate
Ask your friend to menulisakn a large number of 5 digits or more, then add up the numbers and reduce the number of friends had written to the sum of the numbers. Mntalh to your friend to cross out one number from the number of reductions. Finally, ask your friend to mention all the numbers not crossed out one by one slowly. You will soon be the number of the scratch your friend.
The secret as follows. When your friend mentions the numbers, in the memory immediately add the numbers, and multiples of this amount is reduced next 9 equal to or greater than this amount. For example the amount you get is 21, the next multiple of 9 greater than 21 is 27. next, 27 minus 21 equals 6. number 6 is what crossed your friend.
Selected numbers 836946 - 36 = 836910
36 = (8 + 3 +6 +9 +4 +6) = 36
83(6)910
All the numbers add up unless the number 6 = 21. the next multiple of 9 greater than 21 is 27. then 27-21 = 6, the number dropped by a friend.
