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This video is provided as supplementary material
for courses taught at Howard Community College and in this video
I want to do a couple of basic examples of calculating drug dosages.
So here's the first problem. The order reads
600 milligrams. The tablets contain 200 milligrams.
How many tablets should be given?
So we're going to start out with the order,
that's 600 milligrams. That's going to be the beginning of the left side
of an equation. The right side of the equation
is going to tell me how many tablets should be given.
So I'm going to leave a space for the number of tablets,
and I'll just write the unit, which is tablets.
I know that each tablet contains 200 milligrams.
I'm going to take that information and
make a fraction - the faction is going to be
1 tablet -- that's the numerator --
over how much each tablet contains --
200 milligrams. And since I'm dealing with fractions and I might want to
take the 600 milligrams
and make that into a fraction. I'll just put that over 1.
You don't have to do that, but if it makes it easier for you, you can.
When I'm dealing with fractions, I want to multiply
all the numerators -- multiplying across multiply all the denominators.
But before that I want to see if I can simplify what I've got.
Well, I've got milligrams in both the numerators and denominators,
so I'm going to cancel out the milligrams. I've got 600 and 200.
So I could divide both these numbers by 100.
So we'll turn that 600 into a 6 by crossing at the two zeros,
and we'll turn the 200 into 2 by crossing out the two zeros.
I've got a 6 and a 2. I could simplify that, I could divide both
those numbers by 2. So let's divide the 6 by 2
and get 3. I'll divide the 2 by 2 and get 1.
And my denominator has just a 1
and a 1 in it, so I won't have to worry about the denominator.
If I multiply the numerators across
I get 3 times 1 tablet, and that's going to mean I've got
3 tablets.
So basically what I did when I set this up
was write, on the right side... I'm sorry...
on the left side, the amount that was ordered. That was a 600 milligrams.
On the left side of the equation I wrote the units that I was going to be
dealing with -- tablets.
I took the remaining information, one tablet contains 200 milligrams,
made a fraction and then before multiplying I cancelled out whatever I
could.
Then Imultiplied across and ended up with my answer.
Here's another one. The order is for 150 milligrams.
Scored tablets on hand contain 80 milligrams. Remember if it's a scored tablet
it means
if you need to you can cut it in half. How many tablets should be given?
So the order was for
150 milligrams. So I'll write 150 milligrams
and I'll put that over 1, since I'll be dealing with fractions.
On the right side of my
equation, I'll leave a space for the answer. And the unit is going to be tablets.
So it'll be some number of tablets, and then my last bit of information
is that one tablet or each tablet contains 80 milligrams.
So I'll make a fraction, 1 tablet
over 80 milligrams.
And before multiplying, I'll see what I can simplify.
I can simplify the units. I'll cross out the milligrams
in this numerator and this denominator.
I've got 150 as a numerator
and 80 as a denominator. so I could divide both of those by 10.
That leaves me with 15 and 8. I can't simplify this anymore,
so multiplying across I'm going to get 15,
15 tablets, and I've already got the 'tablets' written
and that's going to be over what I get when I multiply the denominators,
which is just 8. So the 15 over 8
tablets. Let's take that fraction... we could put into a calculator
and that would tell us that was equal to 1.875
tablets. At this point we have to think about
whether we want to round the up or down or whether we have to cut the tablets in half.
So let's remember the rules for rounding tablets that we can cut in half,
scored tablets.
So if the decimal part of our answer
is between 0 and 0.24,
then we just round down. If the decimal part
of the answer is between 0.25
and 0.74 then we give a half a tablet.
So that would be 1 1/2 tablets. If the decimal part is between
0.75
and 0.99 then we would round up.
Well, the decimal part was 0.875,
so that would mean that we round this answer up and we're going to
end up with 2 tablets.
So once again, the basic approach was: I write down the amount ordered
on the left side of the equation.
The right side is the units that I'm dealing with
and then I take
the number of milligrams that are in a tablet and I make a fraction.
I cancel out whatever I can. I multiply across,
turn the answer into a decimal if it's not a simple answer,
and then decide what rounding I have to do.
Okay, that's about it. Take care, I'll see you next time.