Question

The area of the base of a right circular cone is 78.5 cm square. If the height is 12cm find its volume and the curved surface

Answer 1

hope this will help you✌

Answer 2

$\Large{\textbf{\underline{\underline{According\:to\:the\:Question}}}}$

${\boxed{\sf\:{Area\;of\;Base}}}$

= 78.5 cm²

Height (h)

= 12 cm

Assumption

Radius be “r cm”

Also,

Slant Height = l cm

As we know that :-

Area of base = πr²

78.5 = 3.14 × r²

$\tt{\rightarrow r^2=\dfrac{78.5}{3.14}}$

$\tt{\rightarrow r^2=\dfrac{7850}{314}}$

r² = √25

r = 5

$\tt{\rightarrow Volume\;of\;Cone=\dfrac{1}{3}\times\pi r^2h}$

$\tt{\rightarrow\dfrac{1}{3}\times 3.14\times(5)^2\times 12}$

= 3.14 × 25 × 4

= 314 cm³

Hence

l = √h² + r²

l = √{(12)² + (5)²}

l = √(144 + 25)

l = √169

l = 13 cm

Also,

CSA of Cone = πrl

= 3.14 × 5 × 13

= 204.1 cm²