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.