def times_n(n)
lambda { |x| x * n }
end
times_ten = times_n(10)
times_ten.call(5) # => 50
times_ten.call(1.25) # => 12.5
circumference = times_n(2*Math::PI)
circumference.call(10) # => 62.8318530717959
circumference.call(3) # => 18.8495559215388
p [1, 2, 3].collect(&circumference)