Number gymnastics

In Math this afternoon, we played a mental math game called "number gymnastics."  The students were really challenged by it and wanted to play past the time we had.  Here is an example so you can play at home.  My number has 1 as the first digit and 5 as the second (15), now reverse the digits (51), now add 1 (52), reverse the digits (25), and take away 2 (23).  Have fun playing!