- [Narrator] I have a rectangular prism here
and we're given two of the dimensions.
The width is 2, the depth is 3.
And this height here, we're just representing with an H.
And what we're gonna do in this video is think about
how does the volume of this rectangular prism change
as we change the height?
So let's make a little table here.
So let me make my table.
So this is going to be our height
and this is going to be our volume, V for volume.
And so let's say that the height is 5.
What is the volume going to be?
Pause this video and see if you can figure it out.
Well, the volume is just going to be the base times height,
times depth, or you could say it's gonna be
the area of the square.
So it's the width times the depth,
which is 6 times the height.
So that would be 2 times 3 times 5,
so 2 times 3 times 5, which is equal to 6 times 5,
which is equal to 30, 30 cubic units.
We're assuming that these are given in some units,
so this would be the units cubed.
All right, now let's think about it
if we were to double the height,
what is going to happen to our volume?
So if we double the height,
our height is 10, what is the volume?
Pause this video and see if you can figure it out.
Well, in this situation we're still gonna have 2 times 3,
2 times 3 times our new height, times 10.
So now, it's going to be 6 times 10, which is equal to 60.
Notice when we doubled the height,
if we just double one dimension,
we are going to double the volume.
Let's see if that holds up.
Let's double it again.
So what happens when our height is 20 units?
Well, here our volume is still gonna be 2 times 3
times 20, 2 times 3 times 20,
which is equal to 6 times 20, which is equal to 120.
So once again, if you double one of the dimensions,
in this case, the height, it doubles the volume.
And you could think of it the other way.
If you were to halve, if you were to go from 20 to 10.
So if you halve one of the dimensions, it halves the volume,
you go from 120 to 60.
Now, let's think about something interesting.
Let's think about what happens
if we double two of the dimensions.
So let's say, so we know, I'll just draw these really fast.
We know that if we have a situation
where we have 2 by 3 and this height is 5,
we know the volume here is 30, 30 cubic units.
But now let's double two of the dimensions.
Let's make this into a 10 and let's make this into a 4.
So it's gonna look like this,
and then this is gonna be a 4.
This is still going to be a 3,
and our height is going to be a 10.
So it's gonna look something like this.
So our height is going to be a 10.
I haven't drawn it perfectly to scale,
but hopefully, you get the idea.
So this is our height at 10.
What is the volume gonna be now?
Pause this video and see if you can figure it out.
Well, 4 times 3 is 12 times 10 is 120.
So notice when we doubled two of the dimensions,
we actually quadrupled.
We actually quadrupled our total volume.
Think about, pause this video
and think about why did that happen?
Well, if you double one dimension, you double the volume,
but here we're doubling one dimension
and then another dimension.
So you are multiplying by 2 twice.
So think about what would happen
if we doubled all of the dimensions.
How much would that increase the volume?
Pause the video and see if you can do that on your own.
In general, if you double all the dimensions,
what does that do to the volume?
Or if you halve all of the dimensions,
what does that do to the volume?