Help with Math, Please.....

carolinapooh, BSN, RN · Aug 30, 2009

Look at the second problem again. If you have 200,000 units in ONE milliliter, you couldn't possibly have FEWER units in MORE milliliters. Try that one again. Part of learning this stuff is being able to look at your answer and determine if it's even reasonable.

For the first one - you're dead on correct.

Look at your second one again, though. My guess is you set it up backwards.

Snwbdr · Aug 30, 2009

-A patient is to receive Phenergen elixer 25 mg. The bottle is labeled 10mg per tsp. How many milliters should be given?
What I got:2.5?
-Penicillin G Sodium for injection contains 200,000 Units per milliliter. How manu units would there be in 2.5 mL?
What I got:100,000?

first one is right, it's 2.5ml

the second answer is 500,000 units. You take 200,000 units/ml and multiply it by 2.5mL....the ml's cancel out and you're left with 500,000 units

nursejoy1, ASN, RN · Aug 30, 2009

The answer to the first question should be 2.5 tsp, not 2.5 mL. 1 tsp=5 mL, so 2.5 tsp = 12.5 mL as for the second, the other posters were correct

rita.kumar83 · Aug 30, 2009

Thanks, for the reply. At least, I know that I am correct with the first problem. However, I am still a bit confused with the second one, how do you come up with the answer? I still don't get it.....yecks!

carolinapooh, BSN, RN · Aug 30, 2009

200,000 units / 1 mL = x units / 2.5 mL

Solve for x.

And she got me - I missed the units on the first one...sorry...

Little Panda RN, ASN, RN · Aug 30, 2009

-A patient is to receive Phenergen elixer 25 mg. The bottle is labeled 10mg per tsp. How many milliters should be given?
What I got:2.5?
-Penicillin G Sodium for injection contains 200,000 Units per milliliter. How manu units would there be in 2.5 mL?
What I got:100,000?

Remember with your first problem, your answer should read 2.5 tsp or 12.5 mls.

With your second problem you should be using multiplication because the question is asking you "how many units would be in 2.5 mls. You have 200,000 units per ml, so 2.5 x 200,000 = 500,000, so you have 500,000 units per 2.5 mls.

rita.kumar83 · Aug 30, 2009

Thank you very much, this really helps!!!!!!!

sleepyRN2 · Aug 30, 2009

-A patient is to receive Phenergen elixer 25 mg. The bottle is labeled 10mg per tsp. How many milliters should be given?

What I got:2.5?

Note: Use Dimensional Analysis, leaves little room for error, and any errors usually occur in using the wrong conversion factor or factors.

X mL of Phenergen = 25 mg Phenergen X (1 tsp/10 mg) X (5 mL/1tsp)

= 12.5 mL (milliliters) Phenergen

-Penicillin G Sodium for injection contains 200,000 Units per milliliter. How many units would there be in 2.5 mL?

What I got:100,000?

X Units Penicillin G Sodium = 2.5 mL X 200,000 Units/1 mL

= 500,000 Units Penicillin G Sodium

Notice that when you use dimensional analysis, the "wanted" unit should only be the remaining unit as your left over, that is all other units you used to get to your answer disappear. and when this happens, i.e. you ending up with your "wanted" unit in your dimensional analysis set up, then you are pretty much done with the problem. now all you have to do is carefully do your math.

JD1985 · Aug 30, 2009

For the first one I got 2.5 TEASPOONS not MLS

and the second i got 500 000units

sleepyRN2 · Aug 30, 2009

in the first question, it is asking for milliliters, so you have to convert the teaspoon (tsp) to milliliters, which is 1 tsp = 5 mls; that's the question, not teaspoon but it wants it converted to milliliters (mL).

docbkh · Aug 30, 2009

some added dosage support is available here

BTW... I got that link from another supportive member of AN!