The volume of a cylinder is V = pr^2*h, so the volume of the solid cylinder is:
V = p(15)^2*(135) = 30375p cm^3,

so you are right with the volume of the cylinder.

Now, the four right circular solid cones are identical, so the volume of each cone is the same (30375p/4). This gives:
(1/3)pr^2*h = 30375p/4.

Since h = 2r:
(2/3)pr^3 = 30375p/4
==> r^3 = 91125/8
==> r = 45/2.

Therefore, the four resulting cones each have a radius of 45/2 cm and a height of 2(45/2) = 45 cm.

I hope this helps!

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