volume of a cone=1/3 times height times area of base
area of base=area of circle=pi times r^2
r=3
aprox pi to 3.14
height=9
so we have
volume=1/3 times 9 times 3.14 times 3^2
3^2=9
1/3 times 9 times 3.14 times 9
3 times 3.14 time s9
9.42 times 9
84.78
nearest tenth
0.78=0.8
answer is 84.8 ft^3