You receive an order for 1000 milliliters
of D5W to infuse over 12 hours.
The drop factor is 20 drops per mil.
We want to determine the flow rate at milliliters per hour,
and also, the drops per minute.
So, for a quick review,
to determine the flow rate at milliliters per hour,
we take the total volume of the solution in milliliters,
and divide by the total number of hours to run.
Once we find this flow rate,
we can then find the drops per minute,
by taking the flow rate, in milliliters per hour,
multiplying by the drop factor,
and then dividing by 60 milliliters per hour.
So, going back to our example,
to determine the flow rate in milliliters per hour,
we'll take 1000 milliliters,
and divide by 12 hours.
We'll go ahead and use a calculator
to determine this quotient.
Going to have 1000 divided by 12.
Rounding to the nearest milliliter,
the three in the tenths place value tells us to round down,
so this will round to 83 milliliters per hour.
If we are required to perform this quotient by hand,
we'll go ahead and show that.
1000 divided by 12.
10 is too small, so you go to 100.
There are eight twelves in 100.
Eight times 12 is 96, and we subtract.
This difference is four, bring down the zero.
There are three twelves in 40.
Three times 12 is 36, and we subtract.
This difference is four.
We need to go one more decimal place
in order to round to the nearest milliliter,
so we put another decimal point here, move it up,
and now we can add a zero, and bring it down.
Again, there are three twelves in 40.
Three times 12 is 36, and we subtract,
and this difference is four, but we can stop.
This three here tells us to round down,
giving us 83 milliliters per hour.
Now that we have the flow rate in milliliters per hour,
we can find the drops per minute.
To find the drops per minute,
we'll start with the flow rate in milliliters per hour,
so we'll have 83 milliliters per hour,
times the drop factor, which is 20 drops per minute,
and we'll divide this by 60 minutes per hour.
Now, whether we're doing this by hand,
or on the calculator, it's often helpful
to simplify this first.
Notice, 20 and 60 share a common factor of 20.
There's one 20 in 20, and three twenties and 60,
so this is going to be equal to
83 divided by three, drops per minute.
Let's first do this on the calculator,
and then we'll do it by hand.
So, 83 divided by three.
Rounding to the nearest drop,
notice how we have a six in the tenths place value,
which means it will round up.
This will round to 28 drops per minute.
Again, by hand, we would have 83 divided by three.
There are two threes in eight.
Two times three six, and we subtract.
This difference is two, bring down the three.
There are seven threes in 23.
Seven times three is 21, and we subtract,
this difference is two.
We need to go one more decimal place to round
to the nearest drop, so we put a decimal point here,
bring it up to the quotient,
add a zero, and bring it down.
There are six threes in 20.
Six times three is 18.
Subtract, this difference is two.
Well, we can go ahead and stop.
We can see there's a six in the tenths place value,
indicating that we round up to 28.
So, the flow rate would be 83 milliliters per hour,
and the drop rate would be 28 drops per minute.
I hope you found this helpful.