This is an easy half-life calculation because it involves an exact integer of half-lives. 1,104 days is precisely 8 half-lives. After each half-life, one half of the original remains.
So, after 8 half-lives you will have 1 / 2^8 of the original material left.
So we start with 30 grams and 1 / 2^8 =
0.00390625.
We are therefore left with (30 *
0.00390625) or
0.1171875 grams of the original 30 grams of polonium.
