Question 212847
A cylindrical can contains three tennis balls. 
The diameter of each tennis ball is 8cm. 
If the tennis balls fit snuggly against the interior of the can, and against
 the top and bottom of the can, how many cubic centimeters of empty space are in the can? 
Express your answer in terms of pi.
:
r = 8/2 = 4 cm, h = 3(8) = 24 cm
;
Empty space (E) = the vol of the cylinder - the vol of the 3 balls
:
E = {{{pi*4^2*24}}} - {{{3(4/3)*pi*4^3}}}
3's cancel
E = {{{pi*16*24}}} - {{{4*pi*64}}}
:
E = {{{384*pi - 256*pi}}}
:
E = {{{128*pi}}}