I used the tract method to solve this problem. it's easier this way for me. You can see all the factors you need to use. You also use this method when calculating drops per min.

How to set it up: 800 ml 1 hr -------|--------- 12 hr 60 min

Next cancel out the common factors and multiply across.

800ml ------ 720min

Divide and solve. Answer 1.11 ml/min

May 05, 2011

This is not so bad by: Anonymous

or you can do it this way: Change the 12 Hours to mins by mulitplying 60 mins

12 x60 = 720 mins

Divide the volume 800ml by 720min

800 ml/720 min =1.11 ml/min

Feb 28, 2011

Got it! by: Judi

Thanks Keith - I needed that!

Feb 28, 2011

Response to Anonymous by: Judi

I understand how the end result is achieved but here is where I'm stuck: How in the name of heaven do you get 66.7??? I divide 12 into 800 & I get 66.6 - every time. I cannot go any further with the problem until I understand the 66.7. Please help before I am completely bald from pulling my hair out!

Reply (by Keith)

Hi Judi, I don't want you to lose anymore hair over this problem ;)

On my calculator:

800 Ã· 12 = 66.666667

When you're doing these calculations, most of the time you want to round up the 1st or 2nd digit after the decimal.

In this case that becomes:

66.7

What determines the number of places you want to round to (in Chemistry) is how many numbers are in the largest factor of the problem. In this case that number is 800, which has 3 digits in it, so your answer needs to have 3 digits. If we were dealing with 8000, then the answer should be 66.67. These are called significant figures.

As far as dealing with the questions on this site and on the exam, if you are off by 0.1 in your answer, it's nothing to split hairs over since answers are multiple choice. Yet, when you're compounding in the field then it will be vital to be completely accurate.

Feb 24, 2011

Missing a small but important detail by: Judi

Please break this down some more. I keep getting 1.17 ml/minute. How do we arrive @ 1.11 ml/minute? Somebody help!

Feb 12, 2011

ml/min by: Anonymous

800ml / 12 hrs = 66.7 ml/hr divided by 60 mins = 1.11ml/min