Question

2 cones of same base radius 8cm and height 15cm are joined along their base.find the surface area of the shape so formed.

Answer 1

$$\begin{gathered} \mathrm{Radius}\mathrm{of}\mathrm{a}\mathrm{cone}\mathrm{r}=8\mathrm{cm} \\ \mathrm{Height}\mathrm{of}\mathrm{a}\mathrm{cone}\mathrm{h}=15\mathrm{cm} \\ \mathrm{Slant}\mathrm{height}=\sqrt{{\mathrm{r}}^2+{\mathrm{h}}^2} \\ \mathrm{l}=\sqrt{8^2+{15}^2}=\sqrt{64+225}=\sqrt{289}=17\mathrm{cm} \\ \mathrm{Total}\mathrm{surface}\mathrm{area}=2\times \mathrm{CSA} \\ =2\times \mathrm{\pi rl} \\ =2\times \frac{22}{7}\times 8\times 17 \\ =\frac{5984}{7} \\ =854.85{\mathrm{cm}}^2 \end{gathered}$$