If a cylinder of radius 7cm and height 9cm is melted and constructed into a cone of the same radius, what will be the height of this cone?
- A54cm
- B9cm
- C27cm
- D13.5cm
Solution & Step-by-step Explanation
When an object is melted and recast into another shape, its total volume remains unchanged.
Volume of Cylinder=Volume of Cone
Let the radius of the cylinder be r=7cm and height be h
cyl
=9cm.
Let the radius of the cone be r=7cm and height be h
cone
.
πr
2
h
cyl
=
3
1
πr
2
h
cone
Since the radii are identical, πr
2
cancels out from both sides:
h
cyl
=
3
1
h
cone
9=
3
1
h
cone
h
cone
=9×3=27cm
Volume of Cylinder=Volume of Cone
Let the radius of the cylinder be r=7cm and height be h
cyl
=9cm.
Let the radius of the cone be r=7cm and height be h
cone
.
πr
2
h
cyl
=
3
1
πr
2
h
cone
Since the radii are identical, πr
2
cancels out from both sides:
h
cyl
=
3
1
h
cone
9=
3
1
h
cone
h
cone
=9×3=27cm