Question

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

विकल्प

• 84 cm

• 42 cm

• 72 cm

• 140 cm

Answer 1

84 cm

Explanation:

Since, conical toy is made from the rectangular sheet.

∴ Curved surface area of cone = Area of rectangular sheet.

Let smallest length of the paper sheet required be a cm.

∴ πrl = length × breadth

⇒ 227 × 28 × 21 = a × 22

⇒ 22 × 4 × 21 = a × 22

⇒ 88 × 21 = a × 22

⇒ 1848 = a × 22

⇒ a = `1848/22`

⇒ a = 84 cm