Answer: 40.0
Work Shown:
r = 3 is the radius
h = 3 is the height
LA = lateral area of the cone
LA = pi*r*sqrt(r^2 + h^2)
LA = pi*3*sqrt(3^2+3^2)
LA = pi*3*sqrt(18)
LA = pi*3*3*sqrt(2)
LA = 9*sqrt(2)*pi .... exact area in terms of pi
LA = 39.9859464434252 ... approximate area
LA = 40.0 ......... rounding to nearest tenth
I used my calculator's stored version of pi to get the approximate answer.
Note how the slant height L = sqrt(r^2+h^2) which can be shown through the pythagorean theorem.