math calculation assistance please.

Hello guys,

I am in my third semester currently. Today I had my math calculation test. I didn't think it was too bad but i missed it by 1 question. So I need some help. I need to pass the test, otherwise I will not be able to pass medications in clinical. We have a math calculation test each semester. Here is the question I struggled with:

1.Questions that ask at what time should the medication end.

example: 1.An IV of 50 mL of D5W with Ancef 1 GM is to infuse at 100mL/hr. The IVPB started at 0730.

What time will the infusion end?

-How do we calculate these? I saw a similar question on my test for the first time and I put my answer as 0900 but the answer was 0920. What? How? Help? unfortunately, i don't remember the exact work problem but there must be formula or something.Does anyone know a website where I can find problems specifically like this one or can someone give me one to practice.

**Rose_Queen, BSN, MSN, RN** · Aug 26, 2016

What did you do to come up with your answer? If you show your work, we can help you figure out where you went wrong.

na-na · Aug 26, 2016

For this problem, it's 50 ml and it started at 0730. Since it is to be infuse at 100 ml. I was thinking it probably will take 2 hours 1 be infused because 50 is half of 100. It should end at 0830. maybe? Is there a formula to go by, is there a website I can go to find questions like these.

na-na · Aug 26, 2016

For this problem, it's 50 ml and it started at 0730. Since it is to be infuse at 100 ml. I was thinking it probably will take 1 hour be infused because 50 is half of 100. It should end at 0830. maybe? Is there a formula to go by, is there a website I can go to find questions like these.

NICUismylife, ADN, BSN, RN · Aug 26, 2016

50ml infusing at 100ml/hr would complete in 30 minutes, and would end at 0800. Not at all sure how your professors did the math to have it ending at 0920, so the only advice I can give you is to speak with your instructor. Either you're remembering the problem wrong, or they did some really wonky math to get that answer.

na-na · Aug 26, 2016

I was saying 0920 was for another similar problem we had. How did you get 0800 can you explain please?

NICUismylife, ADN, BSN, RN · Aug 26, 2016

I will attempt to show the work here, I generally do these in my head, so it took a sec to remember how to appropriately write it out. :)

1 hr x 60 mins x 50 mL = 30 mins

100 mL 1 hr

Infusion would end at 0800 if begun at 0730

To show how this works with not so even numbers, lets say it's running at 125 ml/hr

1 hr x 60 mins x 50 mL = 24 mins

125 mL 1 hr

Infusion would end at 0754 if begun at 0730

I hope this helps, the formatting is hard to do on the computer.

NICUismylife, ADN, BSN, RN · Aug 26, 2016

I was saying 0920 was for another similar problem we had. How did you get 0800 can you explain please?

Ok, that makes more sense.

**Rose_Queen, BSN, MSN, RN** · Aug 26, 2016

It's a lot like an algebra equation where you are solving for X. In this question, X is the amount of time the infusion will run. See if you can set up an equation where you would solve for X with the information you have. There is no equation that is going to give you a time of day- that requires a second step of adding X to the time the medication was starting.

**Rose_Queen, BSN, MSN, RN** · Aug 26, 2016

I will attempt to show the work here, I generally do these in my head, so it took a sec to remember how to appropriately write it out. :)
1 hr x 60 mins x 50 mL = 30 mins Infusion would end at 0800 if begun at 0730
100 mL 1 hr
To show how this works with not so even numbers, lets say it's running at 125 ml/hr
1 hr x 60 mins x 50 mL = 24 mins Infusion would end at 0754 if begun at 0730
125 mL 1 hr
I hope this helps!