Calling all you math Wizzards.

I have a test on August 27 and much of it will be Dimensional Analysis. I just can't seem to comprehend this. Is there anyone out there who can help me understand this and make it easier for me when it comes test time?

I am not asking for you to do my homework for me, as I have none. But I have to learn how to do this as my professor was not the best.

Can anyone help me learn this?

We're all here for you Janny :)

It's really just algebra but with units rather than numbers. I'll happily walk you through some examples.

Can you do it here on the forum (and not privately just in case you went that way) so we can all learn please?

I've got my Math cur nurses book here at home. I can post some questions. I know how to come to the answers using a method we call D over H times Q, but this does not always work. So, I would like to learn dimensional analysis as my back-up method.

Thanks guys, I'll post a question shortly.

Okay here is one that has me stumped as far as dimensional analysis:

Doctor's order is 1000ml of Lactated Ringer's IV for 6 hours @ 167ml/h

The drop factor is 15 gtt/ml

I got the original flow rate of 42 gtt/min

And

After 4 hours, there are 360 ml remaining; describe your action now.

For the time remaining I got 2 hours

Recalculated flow rate I got 180 ml/h
Recalculated flow rate I got 48 gtt/min
With a 7% variation.

I just can't do this with dimensional analysis. Please show me how to do this using this process.

It is always best when doing calculations like this to write out the units for each of your calculations - then when you do the math you can tell that you multiplied or divided the right values because the units work out to what the question demands.

In this case, the first calculation would be:


167 \frac {ml} {Hr} \ \times \ 15 \frac {GTT} {ml} \ \times \ \frac 1 {60} \frac {Hr} {Min}




= 41.75 \frac {GTT} {Min}


Inserting the term \frac 1 {60} \frac {Hr} {Min} into the equation is like multiplying by 1, but serves the purpose of getting the dimensional units right.
Notice that the units that are shown both as a numerator and a denominator cancel out when multiplied - leaving the units remaining of GTT/Min.

For the second part:



180 \frac {ml} {Hr} \ \times \ 15 \frac {GTT} {ml} \ \times \ \frac 1 {60} \frac {Hr} {Min}
= 45 \frac {GTT} {min}



Hope this helps!

By the way - what's a "GTT"?

Ebaines, I think I am starting to get it. I just cross out the common numerators and denominators being left with the uncommon, which would be GTT and min.

For instance, on the second part, multiply 180 x 15 then divide by 60 (since it is a denominator and an uncommon value) gives me 45.


Gtt is a unit of measurement in nursing for drops.