Alligation pharmacy math

by Jill
(Virginia)

If a physician orders 500mL of 25% dextrose and you have 50% dextrose 1000ml, how much of the 50% dextrose and how much sterile water do you need?

How do I solve this question?

Comments for Alligation pharmacy math

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Use alligation
by: Anonymous

This would be a simple alligation:

25 parts of 50%
25 parts of sterile water

250 ml of each (x2) -- 500 ml

Alligation Math Setup
by: Jerry

Yes, this is a classic Alligation problem. And, here's the setup:

=> First set-up the tic-tac-toe grid:

50 | - | ? (of 50%)
-----------
- - |25 | -
-----------
-0 | - | ? (of 0%)

=> Next, do math to determine parts of each:

50 | - | 25
-----------
- - |25 | -
-----------
-0 | - | 25

=> Then, add all parts
25 + 25 = 50 total parts.

=> Now, divide volume needed by total parts:
500mL ÷ 50 parts = 10mL per part

=> Finally, Multiply parts x value (per part)
25 x 10mL = 250mL

=> So, the answer is 250mL

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