There are several methods of solving this radioactivity problem. One of the easiest is:
= Residual mass
Where n = number of activity =
Given:
Original mass = 5g, exposure time = 200 days , half life = 50 days, Residual mass = ?
Substituting all the given parameters appropriately, we have
n =
n = 4
= Residual mass
= Residual mass
= Residual mass
Residual mass = 0.3125g = 0.31g