X, Y, V = *0..2
EPS = 1e-9
until (n = gets.to_i).zero?
  cafe = n.times.map{gets.split.map(&:to_f)}
  x, y = cafe.first
  d = 50.0
  r = 0.98
  until d < EPS
    farthermost = cafe.max_by{|c| Math.hypot(c[X] - x, c[Y] - y) / c[V]}
    angle = Math::atan2(farthermost[Y] - y, farthermost[X] - x)
    x += Math::cos(angle) * d
    y += Math::sin(angle) * d
    d *= r
  end
  puts "%.8f"%cafe.map{|c| Math.hypot(c[X] - x, c[Y] - y) / c[V]}.max
end