The halflife of a radioactive substance is the time it takes

The half-life of a radioactive substance is the time it takes for the substance to decay to half its original amount. The substance decays to an amount P according to the formula P Poert, where Po is the initial size of the substance, r is the decay rate, and t is the time in years. Find the half-life of a radioactive substance of 60 grams that decays to 30 grams if the decay rate is 13.9%. (Round your answer to two decimal places.) years

Solution

P = Po e^rt

30 = 60 e^(-.139t )

1/2 = e^-.139t

t = ln 1/2 /- .139

t = 4.99

half life = 4.99 years