# Test Your Wits with Numbers

Louisville, KY

OK, it's up to you to figure this out.

Follow the directions. Go to the site shown below. This will boggle your mind...Take your time and follow the instructions. After reading each window, click on the boy in the lower right corner. You will be amazed....and no, I don't know how it's done.
Gary/Louisville

http://www.digicc.com/fido/

Churchill, Victoria, Australia(Zone 10a)

The way it works is as follows. Take any 4 digit number, eg 7164 and add up its digits 7 + 1 + 6 + 4 = 18 then if there is more than 1 digit add them again, 1 + 8 = 9.
Now jumble the original digits, giving say 1746 and add the digits of this number. The digits are the same, so it will also add up to 9.
When you subtract two numbers, the difference of their digit sums will equal the sum of the digits of the difference. The difference 7164 - 1746 = 5418, this has a digit sum of 18, leading to 9. 0 and 9 are equivalent in summing digits!
This all means that the sum of the digits of the difference of the two numbers, will always be 9.
Removing one of them and jumbling the remaining digits gives a number eg 671.
Ti decide which digit had been left out, simply add the digits of the given number, 6+7+1 = 14 > 1 + 4 = 5.
Subtract this from 9 to get the missing digit, ie 5 in the example.
If the difference comes to 0, then the missing digit is either a 0 or a 9 and 0 has been banned so it must be 9.