Students General Students

Published Jun 28, 2004

Hi. I have a question for all of you nursing students who have learned some clinical calculations. I am wondering what method you were taught for solving the problems? I am starting nursing school in August and have been reading Clinical Calculations A Unified Approach by Daniels and Smith. This book teaches dimensional analysis, doing conversions until the resulting answer. For Example:

Order: Sulfisoxazole 0.25g po

Label: Sulfisoxazole 500mg/tab (scored)

How many tablets should be administered?

This is how I have learned to set it up:

0.25g X 1000mg X 1tab

1g 500mg

(Edited to say: this is not letting me set this up right. The 1g should be under 1000mg and the 500mg should be under the 1 tab.)

Answer is .5tablet, or ½ tablet.

How were you taught to work this problem?

Thank you for your time!

Jill

truern

2,016 Posts

I would convert the 0.25 G to mg first since that's how the med is supplied...then set it up:

500 mg/1 tab = 250 mg/X

cross multiply:

500X=250

divide both by the 500 to get the X alone:

500X/500=250/500

X=1/2 tablet

wonderbee, BSN, RN

1 Article; 2,212 Posts

Hi. I have a question for all of you nursing students who have learned some clinical calculations. I am wondering what method you were taught for solving the problems? I am starting nursing school in August and have been reading Clinical Calculations A Unified Approach by Daniels and Smith. This book teaches dimensional analysis, doing conversions until the resulting answer. For Example:Order: Sulfisoxazole 0.25g poLabel: Sulfisoxazole 500mg/tab (scored)How many tablets should be administered?This is how I have learned to set it up:0.25g X 1000mg X 1tab 1g 500mg (Edited to say: this is not letting me set this up right. The 1g should be under 1000mg and the 500mg should be under the 1 tab.) Answer is .5tablet, or ½ tablet.How were you taught to work this problem?Thank you for your time!Jill

I prefer the dimensional analysis method over the ratio method. We were taught the ratio method but a friend taught me DA. I prefer it because every problem is set up exactly the same way. No memorization of different formulas. I like that all you have to remember is basic conversions and to start off with what you want.

I set it up slightly different sort of reversing the order beginning with the unit you want:

You want # of tabs, so:

Tabs = 1 tab x 1000 mg x 0.25 g

500 mg x 1 g x dose

Answer: 0.5 tabs

It's just a little bit of a reverse order

Edited to say that I see you tried to set it up this way but couldn't. It appears I couldn't do it either.

dhudzinski

24 Posts

Hi. I have a question for all of you nursing students who have learned some clinical calculations. I am wondering what method you were taught for solving the problems? I am starting nursing school in August and have been reading Clinical Calculations A Unified Approach by Daniels and Smith. This book teaches dimensional analysis, doing conversions until the resulting answer. For Example:Order: Sulfisoxazole 0.25g poLabel: Sulfisoxazole 500mg/tab (scored)How many tablets should be administered?This is how I have learned to set it up:0.25g X 1000mg X 1tab 1g 500mg (Edited to say: this is not letting me set this up right. The 1g should be under 1000mg and the 500mg should be under the 1 tab.)Answer is .5tablet, or ½ tablet.How were you taught to work this problem?Thank you for your time!Jill

NEED = 0.25 g

HAVE = 500 mg/tab

What you want to know = # of Tabs

Tabs = 1 Tab/500 mg X 1000 mg /1g X 0.25 g = 250/500 = 0.5 tabs

:)

LeesieBug

717 Posts

I am also a big fan of dimensional analysis......you can figure out anything with that, once you get the hang of it!

Tweety, BSN, RN

33,512 Posts

I would have done it similar to above, convert the ordered .25g into mg since that is how the tablit is supplied. .25 = 250 mg. Then in my head I would have seen 250 mg is going to half of a 500 mg tablet.

On paper it would have looked liked:

xtab/250 mg = 1 tab/500mg and cross multiplied to find out the x = .5

cherokeesummer

739 Posts

DA all the way! Dimensional Analysis.

mariedoreen

819 Posts

What a wonderful self-motivated go getter you are OP !! Way to get ahead of the game! ; )

I took a dose math class for nurses and we were taught to do the problem exactly the way you had it set up. Dimensional analysis is definitely the way to go. (Also comes in very handy for all the math in General Chem!)

BTW, If you haven't checked your box yet, there's a wicked-long e-mail in there from me!

janetrette

178 Posts

i use the formula: D (doctor order) x Q [quality]

---

H (have)

so it would be 0.25g x tabs

--------

500mg

1g=1000mg therefore 0.25g is 250mg. just move backwards 3places

and solve... 250mg

---- x tab

cross out the zeros and mg left with

25 5 1

---- = ----- = ----- = and divide....

50 10 2

Jill1215

121 Posts

What a wonderful self-motivated go getter you are OP !! Way to get ahead of the game! ; )Thank you, MD, for bringing to my attention why it is I am studying during my last free summer! I am a go-go-getter! I just hope I am getting it the way I will be taught. There's nothing like teaching yourself something and then having your professor muck it up and teach you the 'right' way. Thanks for all of the input, everybody. I really appreciate it.Jill

Thank you, MD, for bringing to my attention why it is I am studying during my last free summer! I am a go-go-getter! I just hope I am getting it the way I will be taught. There's nothing like teaching yourself something and then having your professor muck it up and teach you the 'right' way.

Thanks for all of the input, everybody. I really appreciate it.

lovinghands

168 Posts

i use the formula: D (doctor order) x Q [quality]---H (have)so it would be 0.25g x tabs--------500mg1g=1000mg therefore 0.25g is 250mg. just move backwards 3placesand solve... 250mg---- x tab500mgcross out the zeros and mg left with25 5 1---- = ----- = ----- = and divide....50 10 2

I also do it in a similiar way:

D (desired) divide by H (have) then multiply V (vehicle, ex: tab)

(D/H) x V

so (250 mg / 500 mg) x 1 tab = 1/2 tab

Ari RN, BSN, RN

2,029 Posts

This is how I learned it:

D.O. 0.25 g P.O

Available: 500 mg/tab Scored

First of all you have to change the Dr. Order from grams to milligrams, because what's available is in mg not grams.

1 g = 1000 mg {I use the decimal change}

Therefore, 0.25 = 250 mg

This is the set-up I alway's use:

250 mg

------- x 1 tab = x tab

500 mg

{Cancel off the 0}

Then divide:

250

---- x=

500

x= 0.5 tab. Remeber to change it to 1/2 tab.

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