A cylindrical container with internal radius of its base 10 cm, contains water up to a height of 7 cm. Find the area of wet surface of the cylinder.

Find the total surface area of an open pipe of length 50 cm, external diameter 20 cm and internal diameter 6 cm.

The radius of a solid right circular cylinder decreases by 20% and its height increases by 10%. Find the percentage change in its:

(i) volume (ii) curved surface area

Find the minimum length in cm and correct to nearest whole number of the thin metal sheet required to make a hollow and closed cylindrical box of diameter 20 cm and height 35 cm. Given that the width of the metal sheet is 1 m. Also, find the cost of the sheet at the rate of Rs. 56 per m.

Find the area of metal sheet required, if 10% of it is wasted in cutting, overlapping, etc.