Divisibility Rules

     I have always known that a number is divisible by two if it ends in 0,2,4,6 or 8. I have also used the divisibility test for 3 by adding the digits and finding out if the sum of those digits is divisible by three. I did not remember, however, that a number is divisible by 11 if the sum of the even-powered places less the odd-powered places is divisible by 11. Multiples of 11 were not focused on as intensely in my elementary years, so I find this divisibility rule beneficial.  In looking at these rules, I found myself wondering about the benefits of  these divisibility tests for students.

     I think of strategies concerning video and board games and the elation from a child when they figure out a new "trick" relating to a game. Students can benefit from learning these divisibility rules because they give students the power to solve these division problems. I know I personally keep trying to solve problems when I know the algorithm or formula that assists in "cracking" the puzzle presented. Knowing that there is more than one method to solve math problems can also benefit students as they choose the methods that work the best for them individually. Here are some of the divisibility rules:

 
Here is a fun divisibility song:

Here are a couple of game sites involving division or divisibility rules:

http://www.mathplayground.com/game_directory.html

http://www.oswego.org/ocsd-web/match/dragflip.asp?filename=slanedivrules

     In summary, I can personally understand the benefits of learning these divisibility rules. When given a large number, the task of finding factors is less daunting because I know the "tricks" for determining if the number is divisible by the numbers on my divisibility chart. I have been given a special "compass" to help me navigate this sometimes tricky terrain of division. My excitement and desire to solve these problems, proving the validity of the rules as I go along, can be shared by my future students. Math instruction can be fun and enjoyable for students when we take the time to teach strategies and tricks!