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2_40.rb
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2_40.rb
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class Gear
attr_reader :chainring, :cog, :wheel
def initialize(chainring, cog, wheel=nil)
@chainring = chainring
@cog = cog
@wheel = wheel
end
def ratio
chainring / cog.to_f
end
def gear_inches
ratio * wheel.diameter
end
end
class Wheel
attr_reader :rim, :tire
def initialize(rim, tire)
@rim = rim
@tire = tire
end
def diameter
rim + (tire * 2)
end
def circumference
diameter * Math::PI
end
end
@wheel = Wheel.new(26, 1.5)
puts @wheel.circumference
# => 91.106186954104
puts Gear.new(52, 11, @wheel).gear_inches
# => 137.0909090909091
puts Gear.new(52, 11).ratio
# => 4.7272727272727275