chemistry
posted by Sara .
The physician has prescribed a medication of 3.5 mg/kg of body weight. If you give 297 mg of medication what is body weight of patient in kg? Is there a converstion formula?

I don't know that there is but you can make one.
3.5 mg/kg x # kg = 297 mg.
Solve for # kg. 
Tell me what you think: I wrote
#kg = 297mg / 3.5 mg/kg the mg's would eliminate each other and you are left with 297 / 3.5 kg = 85 kg. 
Your answer is correct; however, you haven't made a new formula. You've just solved the equation I gave you.

that is very true. What I was asking involves something like this as an example:
30mg/kg*1000g / 1kg* 1g /1000mg
30/kg* 1000/1* 1g/1000
30 * 1000/1000 * 1g = 30g 
You might be thinking of something like this in dimensional analysis. The factor is 3.5 mg/kg (or 1 kg/3.5 mg).
297 x (1 kg/3.5 mg) = 297/3.5 = 85 kg. 
Thanks, That's it!