Hi everyone. Now I ve got this problem, but not a homework. I hope some of you can help. There is a battery say B, and n small bulbs A1, A2...An. I can make a circuit as : B-> A1-> A2....An . I can also change it to B->A2-A1...An . Of course there are many ways to make a circuit so that all the bulbs will be lit. The question here is: how many possible ways are there to make a circuit.