There is a hemisphere hollow from inside in which there is a cone inscribed whose base is the diameter of the hemisphere. If the radius of the hemisphere is 6 cm, then find the ratio of the volume of hemisphere and volume of the remaining part of hemisphere when cone is dug out from it.
There is a hemisphere hollow from inside in which there is a cone inscribed whose base is the diameter of the hemisphere. If the radius of the hemisphere is 6 cm, then find the ratio of the volume of hemisphere and volume of the remaining part of hemisphere when cone is dug out from it. Correct Answer 2 : 1
Given:
Radius of the hemisphere = 6 cm
Diameter of base of hemisphere = Diameter of base of cone
Formula used:
Volume of hemisphere = 2πr3/3
Volume of cone = πr2h/3
As cone is inscribed in the hemisphere so, the height of the cone will be equal to the radius of the hemisphere
Calculation:
Radius of the base of hemisphere = 6 cm
⇒ Volume of hemisphere = 2π × 6 × 6 × 6/3 cm3 = 144π cm3
Now,
Radius of cone = radius of hemisphere = 6 cm
Height of cone = 6 cm
⇒ Volume of cone = π × 6 × 6 × 6/3 cm3 = 72π cm3
Now, Volume of the remaining part = Volume of hemisphere – volume of cone
⇒ Volume of the remaining part = 144π cm3 – 72π cm3 = 72π cm3
∴ Ratio of Volume of hemisphere and Volume of remaining part = 144π : 72π
⇒ 2 : 1
Short Trick:
Radius of both hemisphere and cone is equal and the height of the cone will also be equal to the radius of the hemisphere
So, h = r = 6 cm
Volume of the remaining part = 2πr3/3 – πr3/3 (as r = h)
⇒ Volume of the remaining part = πr3/3
⇒ π6 × 6 × 6/3 = 72π cm3
∴ Ratio of Volume of hemisphere and Volume of remaining part = 144π : 72π
⇒ 2 : 1