Med Math

You don't need dimensional analysis for this problem. You have correctly divided the liter by 125 to discover that it will be used up in eight hours. If all they are asking you is, "When does the next one go up?" and you can see that eight hours from 0800 is 1600 (or 4pm), then you're done. If they want you to tell them when the second one will be done, you then divide the second liter by 80 and see that it will be done in ____ hours, right?

Let me take this opportunity to repeat my rant about memorizing equations (such as dimensional analysis). I know they can be helpful but ONLY IF you can see when you need to use them.

Test writers know that many people will take a question and pull all the numbers out of it and jam them into an equation. Then they put choices in the multiple choice that will result from somebody having done that, even erroneously, because they know their audience. Alas, a portion of that audience can't read questions critically to see that some of the facts listed have nothing to do with the answer sought. Example:

Give miraclecillin 1gm in 250cc 0.9%NaCl over one hour. Miraclecilin comes in a vial labeled "Add 5.6cc for 2gm/6cc." Your IV tubing has a drop factor of 15gtt/cc. How fast do you set your pump?

If you can't read that and realize that the question stem says you're going to give 250cc in one hour, and so the only possible answer is "250cc/hr," then there's a lot of trouble in med math in your future. :) If you have set up a dimensional analysis with 2, 6, 15, 1, 0.9, and 250 somewhere in it ... you're in big trouble.