1. Place 20 objects on a table.
2. Remove any number of items from 1 to 10.
3. The items that remain will be a two-digit number.
4. Find the sum of these two digits
and remove that many more items from the table.
5. Now remove some of the remaining objects, and tell me how many you removed.
Click here to run again
Click here to see why it works
Many thanks to Jaime Garcia Ramirez for helping me with the javascript!