Quote from wannabenursetx
A vial contains 2 GM of powder. After being reconstituted with 4 cc saline, how many mls are needed to administer a 500 mg dose? The answer is 1 cc, but again, can't figure out how to arrive at that.
Don't know if you would be interested in trying to solve this a less mathematical and more verbal way; but, I suspect you are getting hung up on the math to the point you are having difficulty thinking it through.
So, for the above question look at it this way:
The vial contains 2GM of powder & you need to administer 500mg dose; so, 2 GM is the same as 2000mg (converting that to what is asked for in the dose to be given).
Next, looking at the liquid portion, you have 4 cc. The 4 cc in that vial will hold the 2000mg, after being reconstituted.
So, now you will have 2000mg of powder floating around in that 4cc of saline.
Got to administer 500mg dose. But, the full vial of 4cc has 2000mg. 1/2 of that vial is 2cc & 1/2 of the powder floating would be 1000mg. But, you need to give 500mg---and, that wouldn't be 1/2 (1000mg in 2cc), it WOULD be 1/4 of that.
1/4 of 2000mg is 500mg & 1/4 of 4cc would be 1cc.
So, to give the dose of 500mg you would have to draw up and administer 1cc (1/4 of the 2000mg floating around in the 4cc of saline). Try to visualize it.