Question

Yo = 10 mg; The half-life is 100 days.

Answer 1

After 100 days, the amount of the substance will decrease to half its original value, so Yo/2 = 5 mg. The half-life of a substance is the time it takes for half of it to decay or disappear. So, every 100 days, the amount of the substance will be halved until there is none left.

Question is not clear.