Question

Hey, can you guys help me out with this question? I need the workings too.( find the surface area )

Answer 1

▪︎Side 15 cm, 18 cm and x cm form a right angle triangle.

We know that :

`=\tt {hypotenuse}^(2) = {leg}^(2) + {leg}^(2)`

Which means :

`=\tt {15}^(2) + {x}^(2) = {18}^(2)`

`=\tt 225 + {x}^(2) = 324`

`=\tt {x}^(2) = 324 - 225`

`= \tt {x}^(2) = 99`

`\color{plum} =\tt x = 9.9 \: cm`

Thus, x (radius) = 9.9 cm

We know that :

`\color{hotpink}\tt \: Surface \: area \: of \: cone \color{plum}=\pi r(r + \sqrt{ {h}^(2) + {r}^(2) }`

Then, the surface area of this cone :

`= \tt3.14 * 9.9 *( 9.9 + \sqrt{ {15}^(2) + {9.9}^(2) } )`

`=\tt 3.14 * 9.9 *( 9.9 + √(323.01) )`

`=\tt 3.14 * 9.9 * (9.9 + 18)`

`=\tt 3.14 * 9.9 * 27.9`

`= \tt31.09 * 27.9`

`\color{plum} =\tt\bold{ 867.4 \: cm}`

Therefore, the surface area of this cone = 867.4 cm