Surface area and volumes

In a right circular cone, the cross section made by a plane parallel to the base is a...........

• Sphere

• Hemisphere

• Circle

• Semicircle

A solid piece of iron in the form of a cuboid of dimensions (49 cm × 33 cm × 24 cm) is moulded to form a solid sphere. The radius of the sphere is...........

• 19 cm

• 21 cm

• 23 cm

• 25 cm

The radius (in cm) of the largest right circular cone that can be cut out from a cube of edge 4.2 cm is

• 2.1

• 4.2

• 8.4

• 1.05

A metallic solid sphere of radius 9 cm is melted to form a solid cylinder of radius 9 cm. The height of the cylinder is

• 96 cm

• 36 cm

• 18 cm

• 12 cm

A rectangular sheet of paper 40 cm × 22 cm, is rolled to form a hollow cylinder of height 40 cm. The radius of the cylinder (in cm) is

• 7

• 3.5

• $\frac{80}{7}$

• 5

The number of solid spheres, each of diameter 6 cm, that can be made by melting a solid metal cylinder of height 45 cm and diameter 4 cm, is

• 2

• 4

• 5

• 6

If the surface area of a sphere is 616 cm2 , its diameter (in cm) is

• 7

• 14

• 28

• 56

A hollow metallic sphere with external diameter 8 cm and internal diameter 4 cm is melted and moulded into a cone having base radius 4 cm. The height of the cone is

• 12 cm

• 14 cm

• 15 cm

• 18 cm

A metallic cone having base radius 2.1 cm and height 8.4 cm is melted and moulded into a sphere. The radius of the sphere is

• 2.1 cm

• 1.05 cm

• 1.5 cm

• 2 cm

Slant height of cone is

• $h^2+r^2$

• $h^2-r^2$

• $\sqrt{h^2+r^2}$

• $\sqrt{h^2-r^2}$