The volume of a cylinder is (pi) (radius)² (height).
We know the height, but we don't know the radius.
Is there a way we can find it ?
We know the circumference of the base. Maybe that's a clue.
Can you find the radius of a circle when you know the circumference ?
Circumference of a circle = (pi) x (diameter)
18 pi units = (pi) x (diameter)
Divide both sides by pi : 18 units = diameter
Divide both sides by 2 : 9 units = radius yay !
Now we know the radius and the height of the cylinder,
so we can calculate the volume.
radius = 9
height = 30
we'll use 3.14 for pi .
Volume = (pi) (radius)² (height) =
(3.14) (9)² (30) =
(3.14) (81) (30) = 7,630.2 cubic units
Is there a choice close to that ? I'll go up and look.
Yes ! Choice 'C' is 7,630 cubic units. yay !