Bài 25 Volume of a Cube- Thể tích hình lập phương

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Boys and girls ,

Ladies and gentlemen.

Today  we will be finding the volume of a cube.

First  we should probably talk about what a cube is .

A  cube is basically a box that has six congruent or equal squares.

So  all of the squares that form the cube are exactly the same.

So  what do we mean by volume .

So  here we have a three-dimensional object and this is really the first three dimensional object .

We 've been dealing with when we talk about volume it's .

How  much would fill up the entire cube like if we wanted to pour water into this cube.

How much water would fill up the cube.

So volume is all of the space that's taken up by the inside of the cube.

We're going to use volume when we're talking about any three dimensional object.

So we want to find the volume of this cube .

Now you have to know one of your side lights so.

Here this is six inches.

Now remember because this is a cube this is a three-dimensional object.

That 's created by six identical squares nino and a square.

You are.

Face  in the height of the square exactly the same .

So if that's six inches , this is also six inches .

This 6 inches.

This is six inches really all of the lines you see or six inches.

So when we're finding volume and we first want to find the area of our base which is the square that on the very bottom here.

The first thing we want to do is find the area of the square that is the base of the square.

Remember the space of the square is the square that's on the bottom.

But Now we know that one side length of the square is fixed .

So  the other side length of the square also has to be 6.

And  therefore the area of this square will be 6 times 6 or 36 square inches.

 To  find the volume we're going to multiply the area that is the area of the base.

Times  our height which again in this case is going to be another six inches.

So the volume here of our cube is going to be 216 cubic inches or inches cubed.

Whenever  we're finding the volume of a rectangular prism which

is basically anytime,  you have a three-dimensional figure that's contained by rectangles.

You're going to find the volume by length times width times height now.

Because  this is a cube, our length or width and our height all have the same length.

And  therefore we can say that it is our side length cubed or the side length to the third power.

And  now remember ,because we're talking about volume ,our answer always has to be in our units cubed or to the third power.

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