Question

Find the area of the sheet required to make a cylindrical container which is open at one side and whose diameter is 28 cm and height is 20 cm. Find the approximate area of the sheet required to make a lid of height 2 cm for this container.

Answer 1

Diameter = 28 cm

Radius = 14 cm

Height = 20 cm

Curved surface area of the cylinder + area of the base = area of the sheet

⇒ Area of sheet = 2π rh + πr²

⇒ Area of sheet = πr (2h + r)

⇒ Area of sheet = `22/7 xx 14 xx ( 2xx 20 + 14)`

⇒ 22 × 2 × (40 + 14)

⇒ 22 × 2 × 54

⇒ Area of sheet = 2376 sq. cm

Thus, area of sheet required = 2376 cm² 
Area of sheet required to make a lid of height 2 cm will be

⇒ Area of sheet = 2π rh + πr²

= πr (2h + r)

= `22/7 xx 14 xx ( 2xx 2 + 14)`

= 22 × 2 × (4 + 14)

= 44 x 18

= 792

Thus, area of sheet used to make the lid is 792 sq cm.