# Q : 9    A right circular cylinder just encloses a sphere of radius $\small r$ (see Fig. $\small 13.22$). Find                       (ii) curved surface area of the cylinder,

N Nehul

Given,

The radius of the sphere = $r$

$\therefore$ The surface area of the sphere = $4\pi r^2$

According to the question, the cylinder encloses the sphere.

Hence, the diameter of the sphere is the diameter of the cylinder.

Also, the height of the cylinder is equal to the diameter of the sphere.

 We know, the curved surface area of a cylinder = $2\pi rh$

$= 2\pi r(2r) = 4\pi r^2$

Therefore, the curved surface area of the cylinder is $4\pi r^2$

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