find amt of 382-mg sample left at 28 yrs, given A(t) = ....

[charlesjoy]

-0.029t
The decay of 382 mg of an isotope is given by A(t)=382e where "t" is time in years. Find the amount left after 28 years.

(-0.029t) is to the upper right of "e".

Do I multiply -0.029t by 28 and then 382 to the -0.029t power?

 

[Deleted member 4993]

Re: Solve the problem

-0.029t
The decay of 382 mg of an isotope is given by A(t)=382e where "t" is time in years. Find the amount left after 28 years.

(-0.029t) is to the upper right of "e".

Do I multiply -0.029t by 28 and then 382 to the -0.029t power? ......No

follow the method explained in your previous post:

viewtopic.php?f=3&t=33536&p=130262#p130262

 

[Loren]

Re: Solve the problem

-0.029t
The decay of 382 mg of an isotope is given by A(t)=382e where "t" is time in years. Find the amount left after 28 years.

(-0.029t) is to the upper right of "e".

Do I multiply -0.029t by 28 and then 382 to the -0.029t power?

You seem to have A(t)=382e[sup:fzgv0sbn](-0.029t)[/sup:fzgv0sbn].

If t = 28, just plug 28 in place of t getting A(28)=382e[sup:fzgv0sbn](-0.029*28)[/sup:fzgv0sbn] = 382e[sup:fzgv0sbn](-0.812)[/sup:fzgv0sbn]. Now, calculate that. I got a number between 150 and 175 years.

 

[charlesjoy]

Thanks