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.