Question

A solid frustum is of height 8 cm. If the radii of its lower and upper ends are 3 cm and 9 cm respectively, then its slant height is

Options

• 15 cm

• 12 cm

•  10 cm

• 17 cm

Answer 1

`r_1 = 9 "cm"`

`r_2 =3 "cm"`

`h = 8"cm"`

Slant height of frustum , l `=sqrt(h^2 + (r_1 - r_2)^2)`

                                          `= sqrt(8^2 + (9 - 3)^2)`

                                          `= sqrt(64 + 36)`

                                          `= sqrt 100`

                                          `= 10 "cm"`