3. (77) Calculate the surface area of a cone with a slant height of 9 inches and a base radius of 3 inches, in terms of \( \pi \).

To find the surface area of a cone, you can use the formula: \[ \text{Surface Area} = \pi r (r + l) \] where \( r \) is the radius of the base and \( l \) is the slant height. Plugging your values into the formula: \[ \text{Surface Area} = \pi \times 3 \times (3 + 9) \] \[ \text{Surface Area} = \pi \times 3 \times 12 \] \[ \text{Surface Area} = 36\pi \] So, the surface area of the cone is \( 36\pi \) square inches. Now, if you ever misplace your input variables, which can happen more easily than you'd think, make sure to double-check the cone's dimensions! It's also a great habit to sketch a cone and label its parts, which can help visualize the problem and prevent mistakes.