need help

[hethr]

Hi, I'm new here so I'm sorry if I post this in the wrong spot.

Here are some questions I'm having trouble with. I consider myself math illiterate, so please forgive it it's an obvious question and please explain as simply as possible so I understand.

"Drug is 150mg/2mls. What is the smallest concentration of this drug in 1ml?

"Dog needs a dose if 350 mg. Drug comes in 150mg/ml. What us the volume needed to give this dose?

"drug that is 150mg/ml is a _______ % solution?"

Thanks so much to anyone who can help.

 

[tkhunny]

Nursing school, are we?

You must learn "Dimensional Analysis" and "Ratios"

"Drug is 150mg/2mls. What is the smallest concentration of this drug in 1ml?

150mg/2ml = 75mg/1ml -- Just ponder this one for a moment. This is a ratio.

"Dog needs a dose if 350 mg. Drug comes in 150mg/ml. What us the volume needed to give this dose?

350 mg = 1 dose ==> (150 mg / ml) * (1 dose / 350 mg) -- This is dimensional analysis.

"drug that is 150mg/ml is a _______ % solution?"

This one is a little harder. There actually is not enough information. We must first know that it is a solution in WHAT? Density makes a difference. If it's distilled water, so that 1 ml = 1000 mg (essentially), then we can do it.

I consider myself math illiterate

This is just not helpful. Never say it, write it, or think it again. You CAN do it.

 

[mmm4444bot]

Drug is 150mg/2mls. What is the smallest concentration of this drug in 1ml?

I don't understand why they specify "the smallest" concentration. Ideally, the drug should be evenly dispersed throughout the solvent proportional to 150mg per 2ml, so that any amounts withdrawn from the container will have equal concentration. Otherwise, if different withdrawals from the same container come out with differing drug concentrations, how could one determine the amount of medicine they've actually withdrawn? :?

[A] drug that is 150mg/ml is a _______ % solution?

My guess is that they're asking for the weight/volume (w/v) percent, here.

With a weight/volume percent, the units are grams per milliliters (g/ml).

(Drug weight in grams)/(solution volume in milliliters) * 100 = % g/ml solution

They provided the drug weight in mg, instead of g, so convert first.

To convert mg to grams, divide by 1000.

150mg = 0.15g

The weight of the drug in 1 ml of solution is 0.15g

0.15g/1ml * 100 = 15% g/ml

With w/v percents, if you're given the ratio in mg/1ml instead of g/1ml, the shortcut is to divide mg by 10, to get the percent solution.

150mg/1ml = 15% solution

175mg/1ml = 17.5% solution

225mg/1ml = 22.5% solution

350mg/1ml = 35% solution

500mg/1ml = 50% solution

70mg/1ml = 7% solution

5mg/1ml = 0.5% solution

1000mg/1ml = 100% solution

10mg/1ml = 1% solution

et cetera