Array.split

 01 class Array
 02     def split(part)
 03         num = self.length/part.to_i
 04         result = Array.new
 05         for row in 0..(part-1)
 06             result[row] = self[num*row...num*(row+1)]
 07         end
 08         result
 09     end 
 10 end 

a = [1,2,3,4,5,6,7,8,9]
a.split(3).inspect   # => [[1, 2, 3], [4, 5, 6], [7, 8, 9]]