class Counter
    attr_accessor :count

    def initialize
        @count = 0
    end

    def inc_by(value)
        @count += value
    end

    def inc_by_amount(value, amount)
        @count += value * amount
    end
end

counter = Counter.new
counter.inc_by(1)
# counter.count is 1
puts "count is #{counter.count}"

counter.inc_by_amount(2, 5)
# counter.count is 11
puts "count is #{counter.count}"