Hello I'm learning physics and also brushing up on some math (its been 10yrs) and I encountered difficulty in understanding Dimensional analysis. I don't really understand how they know what number goes on top or what goes on bottom. I've read some explaintations but they just confused me more, one for instance was using the example that 1/6th times 6 over 1 = 1, so what? what are they trying to show me here I'm not catching on. If they give me a fairly simple word problem where you have to convert different units I can do it in my head but I would like to understand D.A. in order to solve more complex problems with more ease. Can anyone offer some help?