The half - life period of a radioactive substance is 20 days. What is the time taken for `7//8^(th)` of its original mass to disintegrate ?

Explanation

Half life period = 20 days
In this problem,
`(1)/(2^(n))=("Quantity remaining")/("Initial quantity")`
`=(1)/(8)=(1)/(2^(3))`
`therefore n =3`
`therefore` Time taken to disintegrate
`= n xx` Half life time
`= 3xx20 = 60` days