Question

plz solve the problem its urgent guys

Answer 1

Question - In figure, you see the frame of a lampshade. It is to be covered with a decorative cloth. The frame has a base Diameter of 20cm and height of 30cm. A margin of 2.5cm 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.

=> Height of each of the foldings at the top and bottom = h = 2.5cm

Height of frame = H = 30cm

Let radius of each part = r

Diameter, 2r = 20

=> r = 20÷2

=> r = 10cm

Now,

[Cloth required for covering the lampshade] = [Curved Surface area of top part I] + [Curved Surface area of middle part II] + [Curved surface area of bottom part III]

= 2πrh + 2πrH + 2πrh

= 2π(h + H + h)

= 2πr(H + 2h)

$2 \times \frac{22}{7} \times 10(30 + 2 \times 2.5) \\ \\ \frac{440}{7} \times (30 + 5) \\ \\ \frac{440}{7} \times 35 \\ \\ = 440 \times 5 = 2200 {cm}^{2}$