Question

1. A substance has a half-life of 1.3 minutes. How many half-lives will the substance go through in 20.1 minutes?

Answer 1

The amount of half-lives will the substance go through in 20.1 minutes

$$n=\frac{t}{t_{1/2}}=\frac{20.1\:\rm min}{1.3\:\rm min}=15.5$$