Question

The radius and slant height of a cone are in the ratio 7:4. if its curved surface area is 792 cm², find total surface area *​

Answer 1

Step-by-step explanation:

The ratio of the radius and height of the cone is 4 : 7.

Let the radius of the cone be 4x and the height be 7x

So, 

Curved surface area of the cone = πrl

792 = 22/7*4x*7x 

x² = (792*7)/(22*4*7)

x² = 9

x = √9

x = 3 cm

So, the radius of the cone = 4 × 3 = 12 cm.

height = 3×7= 21

so,TSA area =

$\pi \times r(l + r)$

22/7×12(21+12)

=1,243.44

Answer 2

Step-by-step explanation:

The ratio of the radius and height of the cone is 4 : 7.

Let the radius of the cone be 4x and the height be 7x

So, 

Curved surface area of the cone = πrl

792 = 22/7*4x*7x 

x² = (792*7)/(22*4*7)

x² = 9

x = √9

x = 3 cm

So, the radius of the cone = 4 × 3 = 12 cm.

height = 3×7= 21

so,TSA area =

\pi \times r(l + r)π×r(l+r)

22/7×12(21+12)

=1,243.44