Estimating Length: Metric Units
In this video, we will learn how to
estimate the lengths of different real-life objects by choosing the most appropriate
unit of length and value in metric units. We use millimeters to measure
things which are very small. The point of this pencil measures
about one millimeter. There are 10 millimeters in one
centimeter. We also use centimeters to measure
small things. The width of your index finger is
about one centimeter.
We use meters to measure larger
objects. For example, the length of this
baseball bat is about one meter. And we know that one meter is equal
to 100 centimeters. When we measure in meters, we don’t
use a ruler. Most rulers are only about 30
centimeters long. So we need to use a tape measure
because it’s much longer than a ruler. We use kilometers to measure
distance from one place to another. One kilometer is equal to 1,000
meters. And it takes about 10 minutes to
walk one kilometer.
In this video, we’re going to think
about which is the best unit of measurement to measure everyday items: millimeters,
centimeters, meters, or kilometers.
Which of these is the best estimate
for the length of a soccer field? Is it 100 centimeters, 10
centimeters, 10 meters, or 100 meters?
If we wanted to measure the length
of a soccer field, would we measure using centimeters or meters? The width of an index finger is
about one centimeter. Does a soccer field measure 100
index fingers? No, it doesn’t. And the length of a soccer field is
not 10 centimeters either. Soccer field measures much more
than 10 index fingers.
Would we use meters to measure a
soccer field? We know a baseball bat is about a
meter in length. If we were to lay out 10 baseball
bats in a row, that would be about 10 meters. A soccer field would measure more
than 10 meters in length. How about 100 meters? This is the largest unit of
measurement we have in our possible answers. So the best estimate for the length
of a soccer field is 100 meters. In actual fact, most soccer fields
do measure 100 meters in length. The best estimate is 100
Which of these is most likely to be
the distance between two cities? 44 kilometers, 2,000 centimeters,
or 84 meters.
In this question, we have to think
about the best unit of measurement to use to measure the distance between two
cities: kilometers, centimeters, or meters. Which is the smallest of these
units of measurement? It’s the centimeter. The width of your index finger is
roughly one centimeter. Can you imagine measuring the
distance between one city and another in centimeters? It would take a very, very long
How about meters? If a baseball bat measures one
meter, would we use meters to measure the distance between two cities? We could, but it would take a very
long time. We use kilometers to measure
distances from one place to another. And it takes about 10 minutes to
walk one kilometer. So this is the best unit of
measurement to use to measure the distance between two cities. So the most likely distance between
two cities is 44 kilometers.
Which measurement below is closest
to the length of a pencil? 50 centimeters, one centimeter,
eight centimeters, or 90 centimeters.
In this question, we’re being asked
to estimate the length of a pencil. All of the possible answers we’re
given are in centimeters. If we know that a centimeter is
about the width of your index finger, how many centimeters long do you think a
pencil would be? 50 centimeters, one centimeter,
eight centimeters, or 90 centimeters.
We can probably rule one centimeter
out. A pencil that was one centimeters
long wouldn’t be very helpful to write with. What about 50 centimeters? And we know that 100 centimeters is
equal to a meter. So 50 centimeters is half a
meter. You might have a long ruler in your
classroom or at home which measures 30 centimeters. And this ruler would be much longer
than your pencil. Pencils don’t usually measure half
a meter long. So we can eliminate this as a
What about eight centimeters? If the length of this line is eight
centimeters, then that looks like a sensible estimate for the length of a
pencil. How about 90 centimeters? Well, we know 100 centimeters equal
one meter. So a pencil that was 90 centimeters
in length would be almost as long as a baseball bat. This is not a sensible estimate
either. So the best estimate for the length
of a pencil is eight centimeters.
Why not try measuring your own
pencil? How many centimeters long is
it? So the measurement below, which is
closest to the length of a pencil, is eight centimeters.
What have we learned in this
video? We have learned how to estimate the
lengths of different real-life objects by choosing the most sensible unit of
measurement: millimeters, centimeters, meters, or kilometers.