Lesson Video: Estimating Length: Metric Units Mathematics • 4th Grade

In this video, we will learn how to estimate the lengths of different real-life objects by choosing the most logical unit of length and value in metric units.

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Video Transcript

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 meters.

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 time.

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 possible answer.

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.

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