college algebra

Question

A radioactive substance decays in such a way that the amount of mass remaining after t days is given by the function:  m(t)=13e^-0.015t  where m(t) is measured in kilograms.

a. Find the mass at time t=0.

b. How much of the mass remains after 20 days?

Answer 1

a)

 

Substitute t = 0

 

m(0) = 13e^-0.015(0)

        = 13e⁰

       

We know that any number raised to the zero power is 1.

 

m(0) = 13

 

 

b)

 

Substitute t = 20

 

m(20) = 13e^-0.015(20)

          = 13e^-0.30

          = 9.65