Question

The height of the solid cone is 12cm and the area of the base is 81 π sqcm , find the curved surface area of the cone.[Take π =3.14]​

Answer 1

Step-by-step explanation:

CURVED SURFACE AREA OF CONE = πrl

HERE π=3.14, l=12 cm , r=?

BASE IS LIKE A CIRCLE IN A CYCLINDER.

SO, AREA = πr²

GIVEN AREA=81π

NOW SUBSTITUTE,

81π=πr²

81=r²

r=√81

r=9 cm

NOW C.S.A= πrl

=3.14×12×9=108π=339.12 sq.cm

Answer 2

height 12 cm

base area 81πcm

radius ?

Area of circle=πr²

81π=πr²

r²=81π/π

r²=81cm²

r=√81

r=9cm

l=√h²+r²

l=√12²+9²

l=√144+81

l=15cm

curved surface area of cone =πrl

=3.14*9*15 (using π=3.14)

423.9cm²