Answer:
[tex]30t^4\sqrt{3}[/tex]
Step-by-step explanation:
To multiply square roots, multiply like terms - terms outside with other terms outside and terms inside with terms inside.
[tex]6\sqrt{5t^3} * \sqrt{15t^5} = 6\sqrt{5t^3 * 15t^5} = 6\sqrt{75t^8} = 6*5t^4\sqrt{3} = 30t^4\sqrt{3}[/tex]