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Math. I can't do it.

ugly

ugly

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I don't know what forum this should go in. Maybe it's not even a Bluelight issue. But I know there's some damn good chemists on Bluelight, and they usually know how to do math. Here is a sample math problem:

1. A prescription calls for 100 mg of a drug that you have in a 250 mg/ 5 ml concentration. How many ml of the liquid do you need?

I don't want the answer. I want to understand how to find the answer. I'm completely lost. I read the chapter. It's like reading a foreign language. Here's another math problem.

2. A prescription calls for 0.24 mg of a drug that you have in a 50 mcg/ml concentration. How many ml of the liquid do you need?

If you don't want to make a thread, then don't, it's fine. Maybe someone can inbox me with a tutorial. At this point, you can send me video of how you solve these. I've got dozens of questions to answer. They are due tomorrow. I can't do the math. I can't find a tutor. The instructor already showed me how and I didn't get it and he's not about to show me again.

I'm in serious need of help and there is no help in my world for math trouble. I decided that it won't hurt anything to ask Bluelight, and I might actually find someone on the planet who can make me understand.
 
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Its basic arithmetic.

250mg in 5ml- 250mg/5ml= 50mg. 50mg in one ml, 2 ml (50mg+50mg) for 100mg. Divide the drug quantity by the volume of liquid to get concentration per ml. Go by the volume AFTER adding the drug, as it will raise the volume. IE 100ml, plus 5g of X drug could put you at ~105ml more or less, it depends on the substance.

Same with the second question. Just divide total quantity of drug added, by total volume of solution to get mg per ml. Divide desired dosage by concentration per ml to get ml required for X dosage.

IE-

5mg/ml solution of substance X.

25mg dose required.

25/5= 5ml, or 5mg/ml X 5ml = 25mg.
 
All you need is a table of basic conversion factors (you know, 1 L = 1000 g = 1 kg) and the willingness to painstakingly relearn arithmetic. If you're literally incapable of performing multiplication and division without tremendous difficulty, I seriously recommend a trip to the doctor (if financially feasible). There exists a neurological disorder - really not trying to be offensive here! - called dyscalculia, the result of which is pretty straightforward: One simply cannot perform the logical/computational operations necessary for the development of basic mathematical skills without a disproportionately great expenditure of effort. It's not very common, but it's certainly not rare either. Also, dyscalculia can often point to a more serious underlying neuropathlology, hence my suggestion re. the doctor's visit.
 
ugly said:
I don't know what forum this should go in. Maybe it's not even a Bluelight issue. But I know there's some damn good chemists on Bluelight, and they usually know how to do math. Here is a sample math problem:

1. A prescription calls for 100 mg of a drug that you have in a 250 mg/ 5 ml concentration. How many ml of the liquid do you need?

I don't want the answer. I want to understand how to find the answer. I'm completely lost. I read the chapter. It's like reading a foreign language. Here's another math problem.
Click to expand...

You need to do problems like this by the "factor label" method. It will keep your units straight.

100mg * (5mL/250mg) = 2mL

So you start with the given quantity, 100mg, and multiply it by the concentration ratio. But you need to flip the ratio in a way such that the units cancel. So in this case you would multiply 100mg by 5mL, and the answer to that (including units) is 500mgmL, then you divide 500mgmL by 250mg, and the "mg's" divide out thus canceling each other, leaving your answer in terms of mL. Its hard to communicate this by typing, but hopefully this helps.
 
it has all helped me a little. i'm still so math backward and i only have two more weeks before i take the board exam. mEq is the most hateful thing anyone ever came up with. I hate milliequivalents SO much, I could fall over from it. we took a practice exam today and on the mEq questions, I wrote "NO IDEA" in the answer box.
 
Hi. I have been "lurking" a lot. I recognize "ugly" from a thread about yoga- an activity I should more actively pursue. In
any event, I guess I need to sharpen my math skills at this time as well. When I was in high-school, I was always stoned and
I never did my homework. Needless to say, I got horrible grades in math. I was encouraged to pursue other things. Later, having
gotten a Master's degree in Social Science, but no real job, I decided to take a graduate level Calculus course in pursuit of an MBA.
What was made abundantly clear to me was how much success in mathematics depends upon a proper mindset. I personally needed
a clear head to complete the coursework and score well on the weekly Friday morning 8:00am (Ugh!) quizzes and the two major exams.
Some people really seemed to have a knack for calculus. They breezed through the course regardless of whether they were drunk, or
stoned, or whatever. I think that a lot of it had to do with their not being intimidated by the apparent complexity of problems that with
just a little "analytical thinking" divulged their solution quite readily. So. . . How does one go about becoming an "analytical thinker"?


Firstly, if you truly want to achieve success at mathematics, you have to work at getting your brain in shape through exercises, and
you really have to refrain from things that might compromise your ability to bring your best to the task at hand. I think many people do
poorly at math because they find that it is possible to do 99% of the problem-solving right and still end up 100% wrong. To be successful
at math it helps to give yourself the best possible chance at being correct. Some people can get into the right "problem-solving" frame of
mind while under the influence. In fact, some people can't get into the right "problem-solving" frame of mind unless they are under the influence.
That is not really the issue. I think if one were to do well at answering mathematical questions, it might rightly be said of the person that they
showed some "math-muscle". It sounds "nerdy" and all, ie. "mathletes", but there is a lot of truth contained therein. Work your way up in problem-
solving starting with things you find easy. As things grow in complexity you probably will have to memorize some formulas. -All the ones I have forgotten! Nowhere is the aphorism, "Use it or lose it." more true than in the study of math. Memorizing formulas allows you to solve some otherwise
baffling problems. If you use the formulas enough, over time you will be able to see why they work. You might compare it to driving to a destination
some distance away that you never went to before. You have to get a set of precise, turn by turn directions, and you have to keep referring to the list the first few times you go to the destination. After some number of trips, you know the route and you get to your destination automatically.
If you really want to be good at math, you probably will surprise yourself at just how good you get with a little effort. Then too, you will be surprised
when after not doing math for some time you find yourself in need of a real tune-up. In any event, Good-luck to you. I could use some luck with my
yoga practice.
 
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ugly said:
2. A prescription calls for 0.24 mg of a drug that you have in a 50 mcg/ml concentration. How many ml of the liquid do you need?
Click to expand...

I'll talk you through this one too, maybe you'll see a pattern.

(1st step) 0.24mg * (1000ug/1mg) = 240ug

(2nd step) 240ug * (1mL/50ug) = 4.8mL

you start with your given quantity, 0.24mg, and multiply it by 1000 because there are 1000ug in 1mg (you're just changing the units to micrograms here, because the concentration of the drug solution is listen in micrograms per milliliter) . This means you want to deliver 240ug of the drug. Since it comes in a given concentration of 50ug per every 1mL, you multiply the 240ug by the concentration, but (again) you flip your ratio over so that the "ug" units cancel out leaving your answer in mL.

do you see the pattern there? you take your given quantity and then multiply it by the ratio. the first term in the calculation is always a number with a unit, and the second term is always a number with a unit divided by another number with a unit. the unit in the denominator of the ratio (second term) should be the same as the unit in the given quantity (first term), that way those units cancel out.

you'll get it, just take it step by step.
 
Alright. I'll work on it tonight. I will work on it every night. I have to get it. I have no option.
 
practice, practice, practice. you will get it if you work at it.

if you have any other questions, just ask and i'll talk you through them
 
Roger and Me posed things quite well. These problems basically encompass 2 steps: units need to be equalized, to be made commensurate, and then proportional calculations must be made.

So for problem two, we have, "A prescription calls for 0.24 mg of a drug that you have in a 50 mcg/ml concentration. How many ml of the liquid do you need?"

The problem is that one of our measures of weight is in micrograms, and the other is in milligrams. A milligram is a thousand micrograms. so we can multiple the quantity in the prescription by 1,000 and re-posit the problem as, "A prescription calls for 240 mcg of a drug that you have in a 50 mcg/ml concentration. How many ml of the liquid do you need?". Then, we'll need to set up a proportion to create an equation to determine the volume of drug which will contain the desired dose. Here it is:

240 mcg / X ml = 50 mcg / 1 ml. See how I did that? We know that the desired dose is, but we don't know what the necessary volume is. And then 50 mics / ml is the concentration of solution. The units in the equation are the same on both sides, reassuring us.

To solve a proportion, cross-multiply each side. So 240 mcg times 1 ml = X ml times 50 mcg (240 = 50X). Solve for X. So X = 240/50. Thus, you need 4.8 ml of solution.

To check your work, set up another proportion. Does 240 mcg / 4.8 ml = 50 mcg / 1 ml? I see that it does.

ebola
 
How do you know when to cross multiply? When there is an equal sign between two fraction?
 
I missed this one on the quiz yesterday.
An IV order calls for the addition of CaCo3. You have a 25 ml vial of CaCo3. 4.4mEq/ml. How many ml of this concentrate do you need to add to this IV?
I put " no idea" for my answer. :(
 
^You haven't given enough information to answer, how much CaCO3 are you meant to be adding?
 
ugly said:
How do you know when to cross multiply? When there is an equal sign between two fraction?
Click to expand...
when there is an equals sign between two fractions, that's an equation.

if i asked you how many quarters are in one half, you'd say 2, right? because you just know that kind of thing. well, you can also write it down and work it out:

x / 4 = 1 /2

on the left side, x is divided by 4 (quarters). to get the value of x, you have to multiply the left side of the equation by 4. but this is an equation so, to keep it equal, you have to also multiply the right side by 4:

so x/4 * 4 = 1/2 * 4

so x = 1/2 * 4 (because something 'x' divided by 4, then multiplied by 4 is just itself 'x', right?)

so x = 2

so 2 quarters make 1 half.

i fear, from reading your responses in the thread, that you need to take a step back and work on learning some basic equation solving because, without that, you can't hope to apply that math to the problems you're posting.

something like this might help: http://idiotsguides.com/static/quickguides/math/algebra_101_solving_ratio_word_problems.html

alasdair
 
Multiple Choice. Solve for X. 22 22yearolds times four hours of math equals X mood for ugly?
A. Bad
B. Terrible
C. Truly Fkkt
D. Don't even go near her.












correct answer: D:X
 
this is segueing into p&s territory but you seem to have convinced yourself that you can't - nor will ever be able to - do this? things like that tend to become self-fulfilling prophecies. the great thing about mathematics is that it's very rule-based. there's no room for interpretation. you start with the simple building blocks and build from there.

there was a time when you had no idea what numbers were, right? then you learned what happened when you add 2 and 2. then you learned to multiply (which is just a special kind of adding, right?). then one day you learned division and that's pretty cool.

i think the first thing you need to do is to take a breath and tell yourself that you can do this. then you'll be 3/6 of the way there :)

alasdair
 
As a young neophyte, I was taught not to "cross multiply and solve for x" when doing chemistry problems, but instead to use the 'factor label' method because it makes it much easier to keep track of your units. Either way will work, but factor label is a more versatile method (and I also just personally think it makes the problems easier to solve, just imho) and that's why the cross-multiplying thing is never taught in general chem classes at universities.

But by all means, use whichever method you personally find easiest. The important thing is you find some way to get to the right answer.
 
ugly said:
How do you know when to cross multiply? When there is an equal sign between two fraction?
Click to expand...

Yes. The equal sign is there because you are trying to make the two sides equal.

Code: 
1          x
--   =    --  
5         10

The answer is 2, do you see why? One-fifth and two-tenths are the same fraction. You set up a problem like this when you know the ratio of two things and want to extrapolate that same ratio to a different value.
 
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