Answer:
0.5 g
Explanation:
Given data:
Half life of radioactive material = 30 days
Total mass = 4 gram
Mass left after 90 days = ?
Solution:
Number of half lives passed:
Number of half lives = Time elapsed / half life
Number of half lives = 90 days / 30 days
Number of half lives = 3
At time zero = 4 g
At first half life = 4g/2 = 2 g
At 2nd half life = 2g/ 2= 1 g
At 3rd half life = 1 g/2 = 0.5 g
