For example #12 I solved it setting up with ratios and cross multiplying - because in my mind I'm thinking that it's the same drug (I.e. Dextrose) and if I'm trying to find a certain amount (g) why can't I set up ratios and cross multiply if I know the percentage/concentration of each? - I set up like and solved #12 like:
1) I need 10% which is 10g/100mL = x/1000mL (
total IV is 1L)
X= 100g needed
However I'm SO confused as to when to set up direct ratios like I did above and when I need allegation. Please help if you can my exam is in 4 days and I'm borderline panic attack
My friend, total is
not 1000 ml. The question was tricky.
In hospital, a bag is premade with 1000 ml. You are given that bag. You have two ways:
Way 1: draw out some liquid and add in whatever DEXTROSE WATER OR SALT WATER you need, total must be only 1000 ml.
Way 2: DO NOT draw out some liquid. Just add in whatever DEXTROSE WATER OR SALT WATER you need, total will be OVER 1000 ml.
This question is ASKING Way 2.
Question wrote:
"You must ADD the volumes of the dextrose and NaCl to the 1000 ml of Sterile Water."
With that in mind, let's continue:
In question 11: Because we are adding SALT WATER to make the bag with 60 mEq, we don't know the final volume yet. But, 60 mEq is not dependent on final volume of the bag, then, we can solve with NON-ALLEGATION way.
They want to you make the bag with 60 mEq of salt.
(Just like they ask you to add 3510 milli-grams of salt into the bag.)
In question 12: After adding SALT WATER, now, they want us to add DEXTROSE WATER, in such a weird way that the PERCENT of DEXTROSE is 10 percent of FINAL VOLUME.
At this point, we don't know FINAL VOLUME.
At this point, we don't even know how much volume of DEXTROSE WATER to add.
Therefore, in question where we don't know the final volume like this, and the question ask for PERCENT of ADDED INGREDIENT, we have to use ALLEGATION.
Key to recognize ALLEGATION math question is:
They ask you to make product.
They ask you to add ingredient.
They ask you:
how much of ingredient to get certain PERCENT of Added Ingredient (
in FINAL PRODUCT.)
Let's phrase the question another way. They seem to say this weird sentence:
You have to blindly add ingredient slowly slowly slowly slowly until you get the ingredient to be 10 percent of the final product.
How in the world can I do that?
Physically, we can but that will take forever to add, compute, add, compute.
Therefore, mathematically, we compute with allegation.
Good luck and please come back here to help others after you pass the exam. Thank you very much for your help in advance...
