Polonium-214 has a half-life of 164 s. How many seconds would it take for 8 g of this to decay to 0.25 g?

Question

I need to know how you got the answer also.

Answer 1

You need to do your own homework.

But it'll be at least an hour.

Answer 2

Each halflife decays a progressivly smaller amount so

1st t 1/2 8 -> 4
4-> 2
2 -> 1
1 -> 1/2
1/2 -> 1/4

Which is a total of 5 half lives, which is 164 x 5 = 820 seconds