Can someone help me with these 2 math problems?

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1. Digoxin(lanoxin) 0.125mg is ordered. On hand is Lanoxin 0.5mg/ml howm many Milliliters will be given? Please I need help are al these problems are suppose to be V/T= D

2. Mrs. B is to give her child 6ml of a liquid medication.Her only measuring toll in her apartment is a teaspoon. How many teaspoon of medication should she give?

Can someone go on chat with me to do some one on one tutoring..


1,326 Posts

I don't want to mess you up too much with the way my school teaches us how to do these problems but I think it is much easier. It is called "Dimensional Analysis".

Problem 1

mL = 1 mL/0.5mg x 0.125mg/1

Problem 2

1 Teaspoon is equal to 5mL. Therefore, she would need to give one teaspoon plus a little extra to meet the 6mL order.


1,326 Posts

Does this help or do you need some help breaking the problem down more (moving decimals), etc.


1,326 Posts


I write out the problem like this at the top of the page.

Ordered = 0.125mg

Have = 0.5mg/1 mL

What are you looking to solve? You need to solve for mL so, you write

mL =

Then, plug in the information you have;

mL = (Have) 1 mL/0.5mg x (Ordered) 0.125mg/1


275 Posts

Thats helps some what.. Im just real slow when it comes to this

Specializes in NICU.

This is the way we learned it:

Our formula:

Desired Amount (what the doctor ordered)

--------------------------------------------------- x Volume

Have Available (what you have on hand)

In shorthand, it's


-- x V


So. With the first problem, your doctor has ordered 0.125mg. That is your "desired." You have a vial with 5mg/ml. 5mg is your "have" and 1ml is your volume. When you plug these numbers into the formula, it should look like this:


------------ x 1ml


Then you just divide and multiply. 0.125 divided by 5 is 0.025. The mg's cancel each other out. Then multiply by your volume, so 0.025 x 1ml= 0.025ml. Out of this vial, you would draw up 0.025ml in your syringe to give to the patient.

With problem number two, your desired is 6ml. That is the dose that has been ordered. What you have on hand is a teaspoon, which is 5ml. In other words, your spoon has 5ml for every spoonful, or you could phrase it 5ml/tsp.

Then you just plug that information in to that formula.


----- x 1tsp


So 6 divided by 5 = 1.2 and the ml's cancel each other out. Then you multiply your 1.2 by the volume that you plugged in (1ml), so 1.2 x 1ml= 1.2ml's. You would pour 1.2ml's and this would be 6mg worth of medicine. In this case, you would not (in real life) be able to accurately do this- there's no way to measure the .2 in a regular teaspoon; you would need something calibrated, like a little measuring cup or something.

Does that make sense?

Also, can you tell me what the V, T, and D mean in your formula? Are they the same as the ones I gave you? Let me know if that doesn't make sense to you. It does take practice. :>)



1,326 Posts

I think V/T=D usually means Volume over Time = Dosage which would not be right in this type of problem.

Perhaps it means something else?

maire, ASN, RN

1,173 Posts

Specializes in Adult Med-Surg, Rehab, and Ambulatory Care.

Algebra! Or ratios, depending on how you want to look at it.

0.5mg/1mL = 0.125mg/xmL

You need to know how many ml you need so solve for x!

5mL/1tsp = 6mL/xtsp

Ditto above, solve for x!

Helps to know measurements, i.e. 5mL = 1 tsp

Hope this helps!

maire, ASN, RN

1,173 Posts

Specializes in Adult Med-Surg, Rehab, and Ambulatory Care.

Looks like a few of us posted within moments of each other. LOL So many helpful people! :)


1,326 Posts

Born2B, it's no problem, take your time. It is important for you to understand how to do these types of basic problems so that you will be able to understand how to do more complex ones later on.

Specializes in NICU.

Oh! Well, in that case...that's a formula used to calculate infusion rates, say, for IV's or for medications that you may be putting over a syringe pump. Basically, that one tells you how long something should take to infuse an at what rate you should infuse it.

For instance, if the MD orders 1000cc's of D10 and says she wants it run over six hours. You'd take your volume (1000cc's) and divide by the time (6 hours), which is 166.666etc. You'd round this off to, say, 166.7cc's, and this is your "dosage", or the amount per hour you'd be running the IV at.

Did the instructor say she wanted that formula used? If so, I'm confused because it doesn't apply to those types of calculations. :>)

Specializes in NICU.

Brilliant minds think alike. :D

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