Question

A radioactive substance decays exponentially. A scientist begins with 150 milligrams of a

radioactive substance. After 40 hours, 75 mg of the substance remains. How many milligrams will
remain after 60 hours?

Answer 1

We are given

Scientist begins with 150 milligrams of a radioactive substance

so,

we can use formula

we can plug Po=150

After 29 hours, 75 mg of the substance remains

so, at t=29 , P=75

we can plug it

now, we can solve for k

now, we can take ln on both sides

now, we can plug it back

and we get

we can plug t=33

we get

..............Answer

Explanation: