Two months later 13.8 milligrams of the barium-131 still be radioactive.
<h3>How is the decay rate of a radioactive substance expressed ? </h3>
It is expressed as:

where,
A = Amount remaining
A₀ = Initial Amount
t = time
T = Half life
Here
A₀ = 0.50g
t = 2 months = 60 days
T = 11.6 days
Now put the values in above expression we get



= 0.50 × 0.0277
= 0.0138 g
= 13.8 mg [1 mg = 1000 g]
Thus from the above conclusion we can say that Two months later 13.8 milligrams of the barium-131 still be radioactive.
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Question: Suppose that 0.50 grams of ban that 0.50 grams of barium-131 are administered orally to a patient. Approximately many milligrams of the barium would still be radioactive two months later? The half-life of barium-131 is 11.6 days.