Triangular Pyramid

volume of a prism is 1/3 area of base triangle * height= 1/3 * 1/2 *4 * 5 * 3 = 10. required ratio = 10: 3 *4 *5 = 1:6

$\text{volume of cuboid=length * width * height} = 3*4*5=60$

$\text{volume of pyramid}=\dfrac{1}{3} * \text{area of the base * height} = \dfrac{1}{3} * \dfrac{1}{2} * 3*5*4 = 10$

$\text{ratio of volumes} = \dfrac{10}{60} = \dfrac{1}{6}$

The desired answer is $\boxed{1:6}$ .