00:01
So you're being asked to find the area, the one surface area and volume.
00:06
So first let's do the volume.
00:09
If you have a cylinder, so you're looking for how much space it takes inside.
00:19
And then the surface area, again, of the cylinder is how much is it taking if you wanted to wrap this up.
00:33
So surface area is wrap.
00:36
So if you're going to wrap it, how much paper you're going to use? and the volume is space it takes, including the inside.
00:49
So how many cubes would it fit inside? so we are given the diameter for this is nine, and the height of this is also nine.
01:00
So i don't really memorize formulas, but except for the basic ones.
01:05
So the area of a circle is high r square.
01:12
So now r is your whole radius.
01:15
In this case, your radius.
01:18
Is 4 .5 because your whole diameter is 9.
01:21
So if you have that circle, you want it nine times.
01:25
So that's one way that i kind of memorized.
01:30
But i didn't memorize, i just memorized the circle.
01:33
So the circles, and you're going to do that nine times.
01:37
So not area, volume.
01:44
So this is my volume formula or a cylinder.
01:48
So in this case, my r, again, is 4 .5, because i only want the radius, i square that and multiply this times pi, times my height is nine.
02:04
So then if i put all this into the calculator, you're going to get 4 .5 squared times 9 times pi...