Question

The curved surface area of a right circular cone is 12320 cm 2 . if the radius of the base is 56 cm, find its height.

Answer 1

Given that radius of cone = 12320cm^2.

We know that curved surface area of a cone = pirl.

GIven that curved surface area of a cone = 12320.

$\pi$rl = 12320

22/7 * 56 * l = 12320

22 * 8 * l = 12320

176l = 12320

l = 12320/176

 = 70.

We know that height of the cone h =  $\sqrt{l^{2}}-\sqrt{r^{2}$

                                                          =  $\sqrt{70^{2} -56^{2}$  

                                                          =  $\sqrt{4900-3136$

                                                          =  $\sqrt{1764$

                                                           = 42.

Therefore the height of the cone = 42m.