Calculating pi using the Monte Carlo method

pi.rb

r = 5
points_total = 0
points_inside = 0

loop do
  points_total += 1
  x, y = rand * r * 2 - r, rand * r * 2 - r

  points_inside += 1 if (x ** 2 + y ** 2) < (r ** 2)
  puts "#{points_inside}/#{points_total}: pi == #{4 * points_inside / points_total.to_f}" if points_total % 10000 == 0
end