The doctor orders a medication as #"5.00 mg/kg"# of body weight. The dosage the nurse gives the patient is #"425 mg"#. How much does the patient weigh in pounds?
You have a little mor econverting to do to solve this one.
You know that the drug dosage is set to
To start, you can convert the dosage from miligrams per kilogram to miligrams per pound by using the conversion factor
#"1 kg" ~= "2.2046 lbs"#
This means that you have
#5.00"mg"/color(red)(cancel(color(black)("kg"))) * (1color(red)(cancel(color(black)("kg"))))/"2.2046 lbs" = "2.268 mg/lbs"#
So, your patient needs 2.268 mg of the drug per pound of body weight. This means that if you supply 425 mg, his body weight must be
#425color(red)(cancel(color(black)("mg"))) * "1 lbs"/(2.268color(red)(cancel(color(black)("mg")))) = "187.39 lbs"#
Rounded to three sig figs, the number of sig figs you gave for the dosage and mass of drug administered, the answer will be
The patient weighs
Medication mass/body mass:
Just over 187 lb
But you want the weight of the patient in lb, so you need to build in the conversion
Therefore the final equation is:
Plug in the numbers and you get 187.43 lb.