2) Now, do two diagonal calculations to get the difference between what you have and what you want and write the answers in the right hand top and bottom. You may have one negative number, but always write it as positive.
3) What you have done is determine how many parts of each formula to use to arrive at the desired formula..
4) Looking at the "Parts", you see that we get 25:45. To make things easier, go ahead and reduce that fraction down to its lowest form..
5) Now you know that you need 14 total parts.
6) Take the number of Parts for the first formula (the 70%) and divide it by the total number of parts. 5 parts ÷ 14 Total Parts = .36 Then, take the amount of milliliters you need and multiply it by that. If a physician orders 25% dextrose 1000ml and all you have is a Liter of 70% dextrose, how much 70% dextrose and how much sterile water will be used ?1000ml X .36 ------- = 360ml (of the 70%) 7) Then, to figure out the rest of the solution, make up the difference with the other parts (the 00%)1000 Total ml- 360ml (of the 70%) --------- = 640ml (of the 00% / Sterile Water) FINAL ANSWER
This is how it might look on the Exam: A. 750ml of 70% / 250ml Sterile Water B. 440ml of 70% / 560ml Sterile Water C. 360ml of 70% / 640ml Sterile Water D. 250ml of 70% / 750ml Sterile Water
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