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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.
Solution
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.
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