Rationalize the denominator. Assume that all expressions under radicals represent positive numbers.

The square root of 3y^4 to the third root divided by the square root of 15x^4 to the third root.
Here is what I have so far:
I multiplied. The square root of 100x^2 to the third root divided by the square root of 100x^2 to the third root= the square root of 300x^2y^4 to the third root divided by 10x^2.
Now I'm not sure what to do because I keep getting the wrong answer.
Thanks for the help.