Question

If you get an order to give a patient 1500mg of drug X and your stock of drug X is 300mg/20mls how many mls would you give the patient?

Answer 1

100 mL

Step-by-step explanation:

Create an equation.

300mg ? mL 1500 mg

----------- X ------------- = --------------

20mL 1 1

Solve for the ?

Divide both side of the equal sign by 300mg which will cancel out the 300mg on the left side and have it in the bottom (denominator) of the right side.

Then multiply both sides of the equal sign by 20mL which will again cancel out the 20mL on the left wide but place it in the top (numerator) on the right side so that it now looks like this:

? mL 1500 mg 20mL

------- = -------------- X -----------------

1 1 300 mg

The mg units will cancel out and you are left with just mL.

1500 x 20 = 30,000 and 30,000/300 = 100

So your answer is 100mL

**** another way to do this is to also use a ratio which works out exactly the same. You should use the equation method in general so if you have to convert units you will be able to know how to do that also. But here is how you would do the ration

300mg 1500 mg

----------- = --------------

20mL X

You cross multiply which give you the exact same answer.

300X = (20) x (1500)

X = 30,000/300 or 100 mL