Question

The radius of a cone is 3 and vertical height is 4. find the area of the curved surface.

Answer 1

CSA= 1/3πr²h

so,

= 1/3*22/7*9*4

= 22/21*36

= 22/7*12

= 37.714 units ..

since u didn't mention any unit I have done this way...if cm means add cm in the place of cm.....

Answer 2

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$\boxed{\huge \underline \mathfrak \red{given}}$

${ \rm{the \: radius \: of \: a \: cone = 3 \: and \: height = 4}}$

$\boxed{\huge \underline \mathfrak \green{to \: find}}$

$\: \: \: \: \: \: { \rm{the \: curve \: surface \: area \: of \: cone}}$

$\boxed{\textbf{ \large \underline{ \blue{solution}}}}$

${ \rm{as \: we \: know \: }}$

${ \rm{c.s.a = \pi rl}}$

${ \rm{ by \: the \: rule \: of \: pythagoras \: theoram}}$

${ \rm { {l}^{2} = {r}^{2} + {h}^{2} }}$

${ \rm{{l} = \sqrt{ {3}^{2} + {4}^{2} } }}$

${ \rm{l \: = \sqrt{9 + 16} }}$

${ \rm{l = \sqrt{25} \: \therefore \: l \: = 5}}$

${ \rm{ so \: the \: value \: of \: l = 5}}$

${ \rm{ \therefore \: c.s.a. = \frac{22}{7} \times 3 \times 5}}$

$\: \: \: \: \: \: \: \: \: \: \: { \rm{ = \frac{330}{7} }}$

${ \rm{c.s.a \: = 47.14}}$

${ \rm{ \large{so \: the \: curve \: surfce \: area \: is \: 47.14}}}$