Question 572538
After one half life, 1/2 of the original amount is left. As another half life passes, the amount left is halved again. So, after 2 half lives, you have 1/4 of the original amount left. As yet another half life passes, the amount left is halved again. So, after 3 half lives, you have 1/8 of the original amount left.
So the answer is 3 times 5760 years or {{{highlight(17280)}}} years