Q. 144.1( 11 Votes )

A. 3.5

B. 7

C.

D. 5

Answer :

Given: Dimensions of rectangular sheet: 40cm × 22cm

Height of the Hollow Cylinder : 40cm

Area of the Rectangle is = length × breadth

Curved surface Area of the Cylinder = 2πrh (where r and h are radius and height of cylinder respectively)

Let a_{1} be the area of Rectangle

∴ a_{1} = 40 × 22 cm^{2}

Let a_{2} be the Curved surface area of Cylinder

∴ a_{2} = 2 × π × r × 40 cm^{2}

We know that when area of a surface doesn’t change even if its shape is changed.

∴ a_{1} = a_{2}

⇒ 40 × 22 = 2 × π × r × 40

⇒ r = = = = = 3.5 cm

∴ Radius of the Cylinder is 3.5cm

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