Answer:
12 grams of Iodine-13 was present 16 days ago
Explanation:
Given:
Amount of Iodine-131 sample present now = 3g
To Find:
Amount of Iodine-131 sample present before 16 days = ?
Solution:
W know that the half life of Iodine-131 is 8days
Let the amount of sample before 16 days be X
Then
The X amount Iodine-131 sample will decay ito ist half after 8 days
after 8 days
=> [tex]X \times \frac{1}{2}[/tex]
=> [tex] \frac{X}{2}[/tex]
after next 8 days , i.e., 16 days
=> [tex] \frac{X}{2}\times \frac{1}{2}[/tex]
=> [tex] \frac{X}{4}[/tex]
Now we know that after 16 days we have 3 grams of Iodine-131 sample
So,
[tex] \frac{X}{4}[/tex] = 3
[tex]X = 4 \times 3[/tex]
X = 12
