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Question:

In the figure, you see the frame of a lampside. 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 how much cloth is required for covering the lampshade.

Solution:

Since, the cloth is in the form of a cylinder.
⇒Height, H = 2.5 + 30 + 2.5 = 35 cm (It includes margin)
Radius, R = 20/10 = 10 cm
⇒Cloth required = 2πrH (CSA of cylinder) = (2 × 22/7 × 10 × 35) cm² = 2200 cm²