Explanation:
1 g = 1000 mg
If we have 1 g or 1000 mg in a 15 ml vial, we can represent as the following ratio:
1000 mg : 15 ml
We know we need 250 mg, and we are being asked how much (in ml) to withdraw from the vial, let's say that is x ml;
This can be represented in the following ratio:
250 mg : x ml
These are equivalent ratios, we can formulate the following equation and then simply solve it:
15/1000 = x/250
x = 250 × (15/1000)
x = 15/4 = 3.75
You will need to administer 3.75 ml of medication from the vial.
This method can be used for any equivalenf scenario.
Another method that can be used in this case is to simply consider:
1000 mg is within 15 ml of the vial solution, we only need to administer 250 mg;
250 mg is ¼ of 1000 mg;
So, equally, we need ¼ of 15 ml, which is 3.75 ml.
