Magic Gopher

I saw that Richard Byrne posted about this website.  The Magic Gopher is site that asks you to pick a two digit number and then subtract the sum of the two digits from the original number.  The gopher then asks you to look up the symbol associated with the result and voila the little one  guesses your answer.  The key is that a two digit number say "ab" is mathematical really 10a+b and if you subtract the sum of the original digits you are doing 10a + b - (a + b) = 9a.  If you notice all multiples of 9 on his list have the same symbol.  This could be used as an introductory to algebra by asking your students how the gopher does it or if you are teaching the distributive property.  To see the website click here.