I need help with 18 please

Answer:[tex]V=35.185,8 km^{3}[/tex]Step-by-step explanation:The volume of a cone can be calculated using the following formula: [tex]V=\frac{\pi . r^{2}.h }{3} \\R= radius\\H=height[/tex]We know that the radius is the half of the figure's diameter. In this excercise: [tex]r= 80 km : 2 = 40 km[/tex]Height in this case is 21 km. So supplanting we get: [tex]V=\frac{\pi.(40km)^{2}.21km  }{3}[/tex][tex]V=\frac{\pi.1600km^{2}.21km  }{3}[/tex][tex]V=\frac{\pi.1600km^{2}.21km  }{3}[/tex]We have in total three "km"'s, and that is equal to [tex]km^{3}[/tex]. Remember that when we want to calculate a volume, the unit has to be raised to the third power.[tex]V=\frac{\105.557,5 km^{3}  }{3}[/tex][tex]V=35.185,8 km^{3}[/tex]