I competed in number sense in high school and really enjoyed it!  Math-magic was very helpful for many types of problems, and for that I thank whoever created the website.  However somehow I never came across this specific forum until now, so hello all!

Several weeks after the 2014 UIL academics season I had some spare time and created a slideshow compilation of number sense tricks to help my schoolmates who were interested in competing.  However I've since neglected it and have only recently realized it's pointless to keep the slideshow sitting idly on my computer.  So I uploaded it to youtube and here it is: https://www.youtube.com/watch?v=D-RRzc5oXuU

If you have a number sense problem math-magic has nearly everything, but if you have a problem that isn't on the website maybe it'll be in this slideshow.  Hopefully I was able to help someone, and good luck/have fun to current competitors out there!