In Fig. 13.12, you see the frame of a lampshade. It is to be covered with a decorative cloth. The frame has a base diameter of 20 cm and height of 30 cm. A margin of 2.5 cm is to be given for folding it over the top and bottom of the frame. Find

Explanation

Clearly, the decorative cloth forms a cylinder of base diameter 20 cm and height `= (30 + 2.5 + 2.5) cm = 35 cm`
Thus, r = 10 cm and h = 35 cm
Area of the decorative cloth
= lateral surface area of a cylinder having r = 10 cm and h = 35 cm
`= (2pi rh) cm^(2)`
`= (2 xx (22)/(7) xx 10 xx 35) cm^(2) = 2200 cm^(2)`