text: Take any four-digit number.
  Create a second number by moving the first digit to the 'back of the queue' and moving the rest along.
  
  Try it a few times. Is the answer always a multiple of $11$?
  Can you explain why?
  
  Click below to see what Samira noticed:
  
  "I started with 5 thousands, 2 hundreds, 3 tens and 8 units.
  After I moved the digits along, my new number had 2 thousands, 3 hundreds, 8 tens and 5 units.
  
  I wonder if this can help me explain what's happening?"
  
  Click below to see what Jay noticed:
  
  "I picked 1000 as my first number, so my second number was 0001 and the total was 1001.
  I know 1001 is a multiple of 11 because it is 1100-99, and 1100 and 99 are both multiples of 11."