Answer:
42 days
Explanation:
Half life = 8.4 days
Starting mass = 40.0 g
Time = ?
Final Mass = 1/16 * 40 = 2.5 g
First Half life;
Remaining mass = 40 / 2 = 20g
Second Half life;
Remaining mass = 20 / 2 = 10g
Third Half life;
Remaining mass = 10 / 2 = 5g
Fourth Half life;
Remaining mass = 5 / 2 = 2.5g
Time = Number of half lives * Duration of half life = 5 * 8.4 = 42 days
