Annemarie van Rhijn

The Last Number:

Consider the string 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
Cross out any two numbers in this list and add the difference to the end of the list.
This new number is now part of the list.
Continue the process of crossing out two numbers on the list and adding the difference until there remains only one number.
What can you say about the last number? Explore.