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Metrics using the unit fraction method--
we're going to the same problems that were on the
shortcut method video clip, except now we're going to use
unit fractions instead.
And we're really just to look at the three
most important ones--
the kilo, centi, and milli conversions.
You can do with meters, liters, or grams.
So up here for the fractions, I just have meters in there.
But just replace the m by l or g when you're
using the other units.
1 kilometer is exactly the same as 1,000 meters.
So this fraction equals 1.
100 centimeters is the same as 1 meter, so that
fraction equals 1.
1,000 millimeters equals 1 meter, so this
fraction equals 1.
So the idea here is we're going to take the unit they
were given--
so for example, 7 meters--
and we want to convert to centimeters.
Well, we're going to multiply by 1.
That means we're not changing the value of what we have.
And multiplying by 1, we want to take the unit fraction
that's going to make the meters cancel out.
So meters has to go in the denominator.
And it's going to leave us with the one we want,
centimeter.
Centimeter has to go in the numerator in order to get that
as our leftover unit.
So we look up top for the conversion.
Well, there's 100 centimeters per meter.
All right, we're really multiplying by 1, so it's OK
to do that.
Meters cancel.
7 times 100, 700 centimeters--
and we have our answer.
Skill Builder number 13, we have 15 liters and we want to
go to milliliters.
So we write down what you have, what you're starting
with, times a fraction to make the liters cancel and leaves
us with milliliter on top.
There are 1,000 milliliters in every 1 liter, because a
milliliter is smaller than a liter.
It takes more of it to equal 1 liter.
So that's the unit fraction we want to use there.
Liters cancel, leaving us milliliter--
15 times 1,000, 15,000 milliliter.
And the last one, Skill Builder number 20, we have 30
milligrams or 30,000 milligrams.
And we're going to multiply by 1 again.
And the unit fraction to build a 1 this time, we'll need
milligram on the bottom, because we want it to cancel
out, gram on top, because that's what we want left over.
Milligram is smaller than a gram by 1,000 times.
We need 1,000 milligrams for one gram.
And that's going to make a milligram cancel, leaving us
with a gram.
And if we divide 30,000 by 1,000, we get 30 grams.
So to use this method, you pretty much have to know these
fractions right here.
And sometimes you're going to have to flip them and use the
meter on top, kilometer on the bottom, or meter on top,
centimeter on the bottom.
Sometimes you use them in the format you see them here.
The key is always put the unit that you want
left over in the numerator.
And make sure the unity you want to cancel goes in the
denominator.