I know that the proper length from a person on earth to a certain constellation is 9 light years and that the time spent traveling in a space ship during a one-way trip to the constellation is 12 years. I have been asked to find the velocity and I have been told that I will not need to use a calculator. This has me a little stumped. My thought is that v=d/t so v=9/12 and the velocity is .75c (c is of course the speed of light). That makes sense if I don't need a calculator. This is the only solution I can come up with. Any comments, suggestions, or confirmation would be helpful?