Ruby Float vs. Fixnum gotcha
Be careful when doing some computation with integers (Fixnum in Ruby). If what you want as a result is supposed to be a float (Float) at least one of the operands has to be float as well.
irb> 1/2 => 0 irb> 1.to_f/2 => 0.5 irb> 1/2.to_f => 0.5
