Math Conversion Question

  1. I hope I can explain this correctly. When converting from mg to gr, how do you know when to use fractions vs whole numbers for the answer? The problem is 15 mg = gr_____. The answer that I come up with is gr iv but the answer key has gr 1/4. I am in the first month of a weekend VN program & am becoming very frustrated with the fact that we don't seem to be getting a lot of instruction. Everything seems to be self study. They had us write abnormal assessments but didn't bother to instruct us on how it should be worded. The same with care plans. I guess I can go buy books on assessments & care plans, but for $30,000. for the program, you would think they could supply us with at least some instruction. Sorry, I had to vent & I guess I got off the subject that I originally posted. Any help would be greatly appreciated. TIA.
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    Joined: Apr '07; Posts: 45; Likes: 4

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  3. by   nursein08
    It would be 1/4 because 1 gr=60 mg, so 1/4 of 60 is 15. If it would be 240 mg, then the answer would be gr iv. Hope this helps.
  4. by   locolorenzo22
    ok, this isn't the best way to post something...but here goes....
    You know that 1gr=60 mg, right? so if you have 15mg....you simply take and divide both sides by 4...to come up with 1/4gr=15mg....that's it....
  5. by   Daytonite
    hi, sports2245!


    by dimensional analysis (factor label method) this problem would be worked as follows where you want to cancel out the label of "mg" and end up with the label of "grain" (these are all fractions with word labels that you manipulate so that when they are multiplied together specific labels will be "factored out", or cancel themselves out, because they appear in a numerator with a matching label in a denominator somewhere. each conversion factor is actually an identity that can be reduced to the number "1". in effect, you are multiplying 15 mg, the quantity on hand, by the number 1, a tricked out number 1, that is going to give you a new expression of the same 15 mg quantity, but this time in terms of grains):
    15 mg/1 x 1 grain/60 mg (conversion factor) = 15/60 grain, or 1/4 grain (after reducing the fraction)


    [the label of "mg" on the number 15 in the numerator of the first fraction and the label of "mg" on the number 60 in denominator of the second fraction factor out (cancel each other out). the only other label left is "grain" which is what you want, and it is in the numerator which is also what you want. also left are two fractions with numbers that you need to multiply together and then simplify, or reduce, to lowest terms. with this method you can flip numerators and denominators when setting these problems up in order to cancel out the labels. you can easily do it with the conversion factors because they always represent a tricked out number "1". 1/1 is always the same as 1/1, so 1 grain/60 mg is the same as 60 mg/1 grain. the trick with dimensional analysis is that you want your final answer to contain the correct labels in the final numerator and denominator positions. thus, you sometimes have to go back and flip your fractions in the series you set up to multiply in order to end up with the result you want. the actual performance of the mathematics are secondary to getting rid of the unwanted labels on the numbers. that's why this is also called the factor label method.]
    now, time for a little refresher on day 1 basic concepts of math, the real number system. there is a hierarchy of the real numbers. it goes like this:
    1. the natural numbers (the ones you use to count with, like 1 , 2, 3 oranges)
    2. whole numbers (all the natural numbers + zero), so 0, 1, 2, etc.
    3. integers (all the whole numbers + negative numbers), so -2, -1, 0, 1, 2
    4. rational numbers (integers + everything in between, but the denominator of a fraction can never be zero) - fractions, decimals and square roots are included in the rational number category
    http://www.jamesbrennan.org/algebra/...ber_system.htm

    now, by convention, when you are given a problem with a number in it that is seeking a number answer, your response should use the same numbering convention that was used in the stem of the question unless you have been instructed to give the answer in a specific way (i.e. express your answer to 4 decimal places). in the case of "15 mg = __ gr", the "15" is a real number that fits into all four of the categories i've listed above. it is only fitting, and per proper protocol, that you give the answer as a real number. since "15" in it's simplest category would be a natural number, and therefore, a real number as well, express your answer as a real number.

    hope i didn't confuse you. using dimensional analysis will get you to the answer on your answer key. but, on a test i would fight like the dickens for the points if i had come up with an answer of 0.25 and it had been marked wrong and there had been nothing said about how the answer was to be expressed.

    i would get away from using roman numerals. it's an archaic system and more and more the recommendation is that they not be used because of the high likelihood of not only making errors with them, but that they can be misconstrued as being something else beside numbers. however, as i always say, double-check this with your instructors.

    to be on the safe side you could always write your answer as "1/4 or 0.25".

    as someone who has been a student off and on throughout my life, i highly recommend supplemental books to help with studying. when i was in my first nursing program i had an older copy of a nursing textbook that my mother found. i used it as a supplemental reference. i found things in there that weren't in my required textbook. it was also just a good alternative resource to read. you are also going to find that a great deal of your learning in nursing is going to be by your own ingenuity. it would be a good idea to find one or more fellow students to interact with on a regular basis. we learn and retain more when we discuss and speak the information out with other people. unfortunately, you just have to make the time to do that. an alternative is to just start giving yourself lectures (talking to yourself) when you think no one is watching! these activities reinforce the learning. they have learned through research that we retain more when we speak it out. that is contrary to what you will hear people say about learning more when they read the information to themselves. i'd believe the researchers.

    something else i would recommend that you do, and this comes from my own experience as a student, is to start a question list every week. when ever you are working on something and a question comes up, write it down on your list right away before you forget it. take this list to your classes on the weekends, get your face in front of the instructor and start reading your questions from the list. have a pen in your hand and start writing down any answers that come your way. there is nothing wrong with doing this. it's really a very intelligent thing to do. i had one instructor who would eventually look at me and say, "don't you have any questions for me today?" another very good piece of advice is to meet with your instructor(s) in their office. be open. ask what books or other materials you could be looking at to help learn xyz material for the class. instructors who realize that students are open and eager to learn will usually tell you what resources to use. in doing so, they are also unwittingly revealing the sources of many of their exam questions, grasshopper. first, though, you really do want to learn the information. having a "what can i do" (positive) rather than a "why does it have to be like this" (negative) attitude as a learner may take a little more energy, but is going to get far better results in the long run, i promise.

    since i also see that you are new to allnurses, let me point out that there are lots of helpful websites for students that are posted within the many "sticky" threads. those are the threads that are always listed first when you pull up the opening page of any forum on allnurses. the two primary forums with student nurse "sticky" help threads are this forum and the nursing student assistance forum (https://allnurses.com/forums/f205/). there are "sticky's" on writing care plans in the nursing student assistance forum that you will want to look at when your time to write care plans comes (https://allnurses.com/forums/f205/de...ns-170689.html) as well as one on this forum (https://allnurses.com/forums/f50/car...-121128-7.html), on the subject of documentation, and on assessment (https://allnurses.com/forums/f205/he...ms-145091.html) where there are links where you may find information on how to write an abnormal assessment. there is a lot to explore and learn from these student forums (https://allnurses.com/forums/f196/)

    see you around! welcome to allnurses!
  6. by   TruDivaRN
    This is how I remember 60mg=gr1. Think of a clock. 15mg, 15min after =gr 1/4, 30mg, 30 min after=gr1/2, 45mg, 45min after=gr3/4.
    Hopes this helps.

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