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Measuring volume - class-VIII
The radius of a cone is $\sqrt2$ times the height of the cone. A cube of maximum possible volume is cut from the same cone. What is the ratio of the volume of the cone to the volume of the cube?
Cube here will be
inscribed in a cone as a square is in isosceles triangle.
Let the height of the cone be $h$
Radius=$\sqrt2 h$
Volume of cone=$\dfrac{1}{3}\pi r^2h$
=$\dfrac{2\sqrt 2}{3}\pi h^3$
Let the side of the cube be x,the top of the cone above it
has the sign $(h-x)$ and radius $\dfrac{x}{2}$
Using properties of similar triangle $\dfrac { \dfrac { x }{
2 } }{ h-x } =\dfrac{\sqrt2 h}{h}$
$=\sqrt 2 x$
$=\dfrac { 2\sqrt { 2 } h }{ 2\sqrt { 2 } +1 } $
Volume of the cube=$\dfrac { 2\sqrt { 2 } h }{ 2\sqrt { 2 }
+1 } $
Ratio of the volume of the cone to volume of the cube=$\dfrac
{ \dfrac { 2\sqrt { 2 } }{ 3 } \pi h^{ 3 } }{ (\dfrac { 2\sqrt { 2 } h }{
2\sqrt { 2 } +1 } )^ 3 } $
$=\dfrac{\pi(2\sqrt { 2 } +1 )^ 3)}{24}$
$=2.35\pi$