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.

A closed cylindrical tank, made of thin iron-sheet, has diameter = 8.4 m and height 5.4 m. How much metal sheet, to the nearest m², is used in making this tank, if $\dfrac{1}{15}$ of the sheet actually used was wasted in making the tank ?

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)

A conical toy tent-house, 28 cm in radius and 21 cm in height, is made from a rectangular sheet of paper 22 cm wide. The smallest length of the paper sheet required is :

1. 70 cm

2. 105 cm

3. 140 cm

4. 280 cm