The total surface area of a hollow cylinder, which is open from both the sides, is 3575 cm²; area of its base ring is 357.5 cm² and its height is 14 cm. Find the thickness of the cylinder.

Two right circular solid cylinders have radii in the ratio 3 : 5 and heights in the ratio 2 : 3. Find the ratio between their :

(i) curved surface areas.

(ii) volumes.

The radius and height of a solid metallic cone are r cm each. The volume of the cone is :

1. $\dfrac{1}{3}πr^2$

2. $\dfrac{4}{3}πr^2$

3. $\dfrac{1}{3}πr^3$

4. $\dfrac{4}{3}πr^3$

The radius of the base of a solid cone is r cm and its height is h cm; its curved surface area is :

1. π × r × $\sqrt{h^2 - r^2}$

2. π × r × $\sqrt{h^2 + r^2}$

3. π × r × (h + r)

4. πr²(h + r)