reverse polish notation calculator

RPNCalculator.rb

class RPNCalculator 
  attr_accessor :value
  
  def initialize()
    @numbers = []
    @value = 0
  end  
  
  def push(num)
    @numbers << num
  end
    
  def plus
    @value = @numbers.pop + @numbers.pop
    push(@value)
    @value
  end
  
  def minus
    n1 = @numbers.pop
    n2 = @numbers.pop
    @value = n2-n1
    push(@value)
    @value    
  end
  
  def times
    @value = @numbers.pop * @numbers.pop
    push(@value)
    @value
  end

  def divide
    n1 = @numbers.pop #4
    n2 = @numbers.pop #3
    @value = n2.to_f/n1.to_f
    push(@value)
    @value
  end
end