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## 4th grade

### Course: 4th grade > Unit 14

Lesson 1: Estimating mass# U.S. customary units: weight

CCSS.Math:

Sal discusses US customary units of mass or weight such as ounces, pounds, and tons. Created by Sal Khan.

## Want to join the conversation?

- isn't the pound is most important to know the whight of the object?(20 votes)
- not always because if a object is less than a pound how would be able to measure it?(8 votes)

- up vote me i up vote u(16 votes)
- Is there a another word for ounce like how 'lb' represents for pound?(10 votes)
- yes. and it is oz(6 votes)

- Aren't ounces and pounds the same measurement of measuring big and small size items?(11 votes)
- how many ounces are in 1122330 pounds(8 votes)
- 17957280

multiply the mass value by 16(5 votes)

- Where did ounces come from?(9 votes)
- i think the spanish or something i got no idea(4 votes)

- How did they come up with pounds and ounces? How did they determined that 16 ounces would be one pound?(7 votes)
- Cause they made it lake that(0 votes)

- why is lb for pounds(6 votes)
- It's from the Latin word for pound, "libra."(5 votes)

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## Video transcript

Let's talk a little bit
about the US customary units of weight. So the one that's
most typically used is the pound,
especially for things of kind of a human scale. And to understand
what a pound is, most playing balls are
roughly about a pound. So, for example, a soccer
ball-- my best attempt to draw a soccer ball. So let's say that this is a
soccer ball right over here. And then of course it has
some type of pattern on it. So you could imagine a
soccer ball is about a pound. So it's roughly one pound. And a pound will
often be shorthanded with this "lb." right over here. So it's about a pound. A football, an
American football, is also a little under a pound. But we could say it
is about a pound, just so we get a sense of what
a pound actually represents. Now, if you want to go to
scales smaller than a pound, you would think about
using the ounce. And the relation between the
ounce and the pound when we're thinking about weight
is that one pound-- let me write this--
is equal to 16 ounces. Or another way of
thinking about it is that 1 ounce is equal
to 1/16 of a pound. And if you want to
visualize things that weigh about an ounce,
you could imagine a small box of matches weigh about an ounce. So a small box of matches
might weigh about an ounce. Maybe a small AA battery
would weigh about an ounce. But that gives
you a sense of it. So if you were to take
16 of these together, they would be about the
weight of a soccer ball. 16 of these things together,
they would be about-- they would be about the weight
of a soccer ball or a football. Now, if we want to
think about weights that are larger than a pound,
then we would go to the ton. And a ton is equal to-- 1
ton is equal to 2,000 pounds. And you have to be a little
bit careful with the ton. We're talking about
the US customary units, and this is where we're
talking about 2,000 pounds. But when we're talking on
a more international level, this is sometimes
called the short ton. There's also a long ton. There's also the metric ton. But here we're talking
about US customary units, which is the short ton. So one ton is 2,000 pounds. And to get a sense of something
that weighs 2,000 pounds, or to get a sense of what
2,000 pounds is like, or what might be measured in tons,
a car is a good example. Your average midsize sedan
would weigh about a little under to a little over
2 tons, so a little under to a little
over 4,000 pounds. If we're talking about a
small van or minivans or vans or trucks, it's going to
be larger than two tons. And if you think
about smaller cars, you think it's going to be
probably around 3,000 pounds. It's going to be
less than 2 tons. So a car is going to be
approximately 2 tons. So hopefully, that
gives you a sense of what units you'd use
in the US customary system for different scales of weights.