Question:
Find the surface area and volume of the figure.
Solution:
1) The surface area:
This shape is composed of a cylinder and hemisphere. Now, we know that the surface area of the sphere is:
[tex]SA\text{ sphere = 4}\pi\text{ }r^2[/tex]
So that, the surface area of the hemisphere would be:
[tex]SA\text{ hemisphere = }2\pi r^2[/tex]
On the other hand, the area of the circle is:
[tex]A\text{= }\pi r^2[/tex]
thus, the surface area of the cylinder would be:
[tex]SA\text{ cylinder = }2\pi rh[/tex]
replacing the data given in the problem in the formulas of the surface area of the hemisphere, area of the circle, and surface area of the cylinder, we get:
[tex]SA\text{ hemisphere = }2\pi(9)^2\text{ = 162}\pi[/tex]
and
[tex]SA\text{ cylinder = }2\pi(9)(12)\text{ = }216\pi[/tex]
and
[tex]A\text{= }\pi(9)^2=\text{ 81}\pi[/tex]
then, we can conclude that the surface area of the given figure is:
[tex]SA\text{ = 162}\pi\text{ + 216}\pi+81\pi\text{ = 459}\pi\approx1441.9\text{ }\approx1442[/tex]
that is:
[tex]SA\text{ }\approx1441.9\text{ }\approx1442[/tex]
2) The volume
The volume of a cylinder is given by the following formula:
[tex]V_C=\pi r^2h[/tex]
and the volume of a hemisphere is :
[tex]V_H=\frac{1}{2}(\frac{4}{3}\pi r^3)\text{ = }\frac{2}{3}\pi r^3[/tex]
thus, the volume of the figure would be:
[tex]V=V_C+V_H=\text{ }\pi r^2h\text{+}\frac{2}{3}\pi r^3[/tex]
Then replacing the data given in the problem in the above formula we get:
[tex]V=\pi(9)^2(12)\text{+}\frac{2}{3}\pi(9)^3\text{ = 972}\pi\text{+486}\pi=\text{ 1458}\pi\approx4580.4\approx4580[/tex]
that is;
[tex]V\approx4580.4\approx4580[/tex]
