How Far is Far? - units, expressed, meters, kilometers
How Far is Far?
units, expressed, meters, kilometers
Motion Unit
A family of elephants has wandered close to a village. They're beautiful, but they eat a lot and can be
dangerous. They couldn't stay. Some scientists shot them with darts that made them sleepy. But these
elephants won't stay sleepy for long. It's your job to move them safely to a place where there's plenty of
food and they won't harm any humans. Here are a few questions you should ask: How many trucks will
you need? How big are these elephants? How far do you need to carry them? Will you be able to do it all
before the elephants become fully awake again?
First, it would help to know how many elephants need to be moved. Let's see. . . one, two, three, four,
five, six, seven elephants. That's a lot of elephants. A unit is what we use to measure the number of
something. It can be anything from seven apples to seven ants to seven eggs to seven elephants to
seven feet to seven seconds. It can also be used to talk about how far away something is, but we will get
to that in a minute. Right now we will need seven more units of something else. What do you think that
is? You're right. Trucks.
Units help us know what we're talking about. I could tell you I have seven of something and you would
have no idea what I was talking about. We use the word expressed to tell what kind of units you are
counting. We could say seven units expressed in elephants. Now that you have that down, we can get to
saving these elephants.
We have seven trucks for seven elephants. But what if one of the trucks is too small? We had better do
some measuring. A meter is about three feet long. That is about the length from the tip of your nose to
the tips of your finger, or a tiger's tail. You can use meters to measure anything from the size of a bus to
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How Far is Far? - units, expressed, meters, kilometers
the size of a playground to the size of an elephant. Let's see, the biggest elephant is. . . wow, 3 meters
tall, 2.5 meters long, and 2 meters wide. As long as we get trucks that can hold that, we're ready to
rumble.
Great, now we have got all of our sleepy elephants loaded onto the trucks. We need to get them far away
from this town so they will not come back and eat all the plants again. In other words, we are not just
going to drive them a few meters away. A kilometer is a thousand meters. We use it when talking about
long distances, like driving or flying. Elephants will walk for days and weeks if they really want to get
somewhere, so we are going to take them to a place that's 500 kilometers away. We don't want the
elephants to wake up before we get there, so our driver will need to drive fast.
The elephants are in a safe place now. You expressed numbers in units to find out how many trucks we
needed. Then you measured the elephants in meters to make sure they fit in the truck. Finally, you
measured the number of kilometers they needed to go before they woke up. The trip went quickly, so
everyone is safe and happy. Without these measurements, you might have had trucks that were too
small, and you might not have given the driver enough time to get the elephants safely away. Everyone
likes a happy elephant.
References:
Math Is Fun. "Metric Length" Math Is Fun, 2010.
<http://www.mathsisfun.com/measure/metric-length.html>
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