If I wasn't Dr. Tom, I'd be Dr. Units. I cannot tell you how many times units are the reason someone gets the wrong answer to a problem. It might be as simple as inches needed to be converted to feet, or the other way around. Or, it is a combination of units like gallons per minute converted to cubic feet per second, and something doesn't cancel. As I say as often as I can, if the units are not right it doesn't matter what the number is. And if it is a predictable error associated with units, then there is a very high probably that the NCEES will make that incorrect answer, answer A, and you now have one less point in your column.
And what makes matters worse, is that most of the solutions in the NCEES Practice Exam have no units, so trying to figure out how the units come out can be very frustrating. And some numbers in these solutions are combinations of unit conversions that I have spent more time than I'd like to admit trying to decipher what they have done. My strongest advice: stay with the basic unit conversions!
There is one thing you typically do not have to worry about relative to units and that is converting between systems, like converting meters to feet or the other way around. About the only time I have seen this required is when horsepower must be converted to kilowatts.
Again, before even thinking about picking up your calculator, make sure the final units are such that they match the units in the exam answers. Then just be careful making the calculation. Remember, you always have time to work the problems you know how to work. - Dr. Tom