Surds and Indices

Question

The mass, m milligrams , of a radioactive substance, present at time t years after first being observed, is given by m=300e^-0.85t .

Given that p milligrams is the amount of the substance that decayed after t years, find an expression for p in terms of t.

 

Ans: p =300(1-e-0.85t)

 

Thank You! :)

Answer 1

Radioactive substance present at t=0

 

m = 300e⁰ =300

 

amount decayed in time t = 300e^-0.85t

 

amount present at time t = 300 - 300e^-0.85t = 300(1 - e^-0.85t)

 

:)