Find the volume of the smaller cone using the ratio of the volumes

the larger cone has a radius of 5m and volume of 8000m^3
the smaller cone has a radius of 2m

Given:
volume of larger cone : 8000 m³
radius of larger cone: 5 m
radius of smaller cone: 2 m
volume of smaller cone: ?

Find the volume of the smaller cone using the ratio of the volumes. 
a / b = c / d where ad = bc

5m / 8000 m³ = 2 m / x
5m * x = 8000 m³ * 2m
5m * x = 16000 m⁴
x = 16000 m⁴ / 5m
x = 3200 m³