The ratio of radii of two cones is 3 : 5 and the ratio of their height is 5 : 4, then the ratio of their volumes is:

9 : 20

Ratio of radii = R₁  :  R₂ = 3   :   5

Ratio of height = H₁  :   H₂  = 5  :   4

Ratio of volumes = \(\frac{1}{3}\) \(\pi \) R₁²H₁   :   \(\frac{1}{3}\) \(\pi \) R₂²H₂

                           =  R₁²H₁   :   R₂²H₂

                           =  (3)² . 5   :   (5)² . 4 

                           = 9 : 20