make10.rb

#!/usr/bin/env ruby

nums = [2, 3, 7, 9]

nums.permutation do |ns|
  %i(+ - * /).repeated_permutation(ns.size - 1) do |ops|
    begin
      x, *xs = ns
      z =  ops.zip(xs).inject(Rational(x)) {|r, v| r.send(*v) }
      p ns.zip(ops).flatten.compact if z == Rational(10)
    rescue ZeroDivisionError
    end
  end
end