Answer:
8.10 days
Explanation:
The half-life of gold-198 (2.70 days) is the time it takes for half the gold to decay.
After one half-life, half (50 %) of the original amount will remain.
After a second half-life, half of that amount (25 %) will remain, and so on.
We can construct a table:
<u>No. of half-lives</u> <u>Fraction remaining</u>
1
2
3
Thus, the gold will decay to ⅛ of its original mass after three half-lives.
∴ Time required = 3 × 2.70 days = 8.10 days