



A cube
is just a square that went 3D.












When we
have stuff in three dimensions, 


we have
another measurement that we can make. 





The
measurement is volume. 





Volume is
the measure of how much stuff 


will fit
inside the shape. 


The
formula for the volume of a cube 


is length
times width times height. 











Another
way to think of this, 


is the
area of the base times the height. 











This
"area of the base" times height idea works for lots of
shapes. 


Anywhere
the object is the same shape on both ends 


and
anywhere in between, we can use this idea. 





Like ... 








Objects
like this are called "right" objects 


because
the sides going up and down 


make
right angles with the base. 











Example: 


Find the
volume of a right cylinder 


with a
radius of 4 and a height of 12 ... 











The first
thing we need to do 


is find
the area of the base circle. 





The
radius is 4 ... 





The area
of the circle is: 


Area
= p
×
4 ×
4



Area »
5.0265 





We use
the »
because we used an approximation for p. 





The
height of the cylinder is 12, so the volume is: 





Volume = 12 ×
base area 


Volume »
12 ×
5.0265 


Volume »
60.318 





copyright 2005 Bruce Kirkpatrick 
