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## 2nd grade

# Getting a sense of inches and feet

Sal describes the difference between inches and feet and helps to decide which unit of measure is best for measuring different objects. Created by Sal Khan.

## Want to join the conversation?

- A cm, or
*centimeter*, is one-hundredth (1/100) of a meter. So if you have 1 meter, you have 0.01 centimeters; and 100*meters*equals 1*centimeter*. When**converting from meters to centimeters**, you just move the decimal toward the left by two place values. And when converting from centimeters to meters, you multiply by 100.

Centimeters is a very small unit of measurement. In the previous video, Sal Khan says that a*centimeter*is only the**width of a fingernail**, while a*meter*is the**length of a guitar**.(14 votes)

- What is the U.S. system?(4 votes)
- The Imperial system, that has inches and feet.(2 votes)

- good point Phillip(3 votes)
- i agree

good point philip(1 vote)

- my son so dumb iq 21 he try to make friends but they call him Ching Chong he eat a wonton but he fat like Kim Jong(3 votes)
- Why does 8feet look deep in the pool?(2 votes)
- the water can change how deep any body of water looks. Also for a pool 8ft is pretty deep.(2 votes)

- A unit is any amount used to measure something against that has a specific name.

feet and inches are units of length.

pounds and ounces are units of mass.(2 votes)

- why are cm. diffrent than meters(1 vote)
- they are different because they are smaller than a meter(1 vote)

## Video transcript

- [Instructor] In this video,
I'm going to introduce you to two units of measuring length. The first is the inch, which
you might have heard about. And you're probably thinking,
"How long is an inch?" Well, if you're familiar with a quarter, a quarter looks something like this. You see George Washington on it. A quarter is almost an inch. So an inch might be something like that. One inch. Another way to think about
it is when I'm looking at my thumb, and I'm a grown man, at least physically (chuckles), my thumb is about two inches in length. So my thumb is about two inches in length. One inch and two inches. Depending on your age,
if you're watching this and let's say you're eight years old, seven or eight years old, your thumb might be closer to an inch or maybe a little bit over an inch. Now the other unit of measurement, you can view it as a bunch
of inches put together. And if you put 12 inches together, you get what is known as a foot, a foot. Now the word foot is used for
many things in our language, including for our individual feet, or the things at the ends of our legs. And I believe, I'm not sure where the unit of measurement
of the foot came from, but they might be related because actually my foot is almost a foot. And in fact, my shoes, and I wear a size, I wear a men's size 10 1/2, my sneakers that I wear are almost exactly one foot. And you can sometimes see it
written as ft, short for foot. Now, clearly not everyone's
foot is exactly a foot 'cause everyone's feet and
shoes have different lengths, but that gets you a sense
of how large a foot is. Another way to think about it, and as I just mentioned, if you put 12 inches
together, you get one foot. 12 inches equals one foot. So let me give you some objects. And I want you to pause
the video and think about, would you measure them in foot or inches or whether the measurements themselves sound like measurements in feet or inches. So if I give you a piece of paper, a regular piece of paper, kind with the holes on
it and the nice lines. So a piece of paper right over here. If I were to tell you that the height of this
paper is 11 something, would that be 11 inches or 11 feet? Well, if was 11 feet, that
would be a huge piece of paper. That would be a piece
of paper taller than me. That would be more of a
carpet than a piece of paper. So a piece of paper, actually a standard piece
of paper is 11 inches tall. Now, if we were to go outside
and play a little basketball, so this is the basketball,
or that's the backboard. And then we have the hoop, the hoop, we have the net, and then we have the post holding it up. Let me draw that in a different color. So we have the post. And this is a standard NBA basketball rim. If I were to say it's 10
something off the ground, is that 10 inches or 10 feet? Well, if it was 10 inches, it would be very easy to
dunk a basketball. (chuckles) Although it might be hard to
fit the basketball in the rim because if the rim was, it
might also be very, very small. That would be more of a basketball goal for an insect of some kind or
for a very, very small mouse. For normal human beings, the standard height of a
basketball goal is 10 feet. The one that they play with in the NBA. At your school, if you're
a little bit younger, you might see a basketball goal that is six feet or
eight feet or nine feet. But the standard ones that the professionals
play with are 10 feet tall. Now let me give you some things, and I wanna decide whether it's better to measure them with feet or with inches. So let's say that I have a swimming pool, say I have a swimming
pool right over here. And that is the pool. Would it be better to measure the length of this swimming
pool in feet or in inches? Pause the video and think about that. Well, a swimming pool is fairly large. It is much larger than even a foot. So you'd think you'd want to measure it, if you had to choose
between feet and inches, you would pick feet. And so this would be a situation where that pool might be, say, 75 feet long. Now, if you were measuring
the length of a mouse, this is a mouse right over here. Not my best drawing of
a mouse with its tail, its feet right over there. Would you be best off
measuring it in feet or inches? A small mouse, a mouse that
could fit in your hand. Well, that's going to be a
good bit less than a foot. So it makes sense to
measure that in inches. I've seen mice that might only
be two or three inches long. So I'll leave you there. Hopefully that gives you a
rough sense of what an inch is, what a foot is, how they're
related to each other, and when you might use one or the other.