SOLUTION: I have no idea how to do this my teacher never taught this type to us. I tried to look in the book but am just so confused with story problems and how to even go about doing this p

Question 441348: I have no idea how to do this my teacher never taught this type to us. I tried to look in the book but am just so confused with story problems and how to even go about doing this problem.
The amount remaining of a certain radioactive substance after t days is
A(t)=A e^(-0.0025t) where A is the begining amount. How much do we need to
0 0
begin with if we want 80 grams after 10 days?
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
The amount remaining of a certain radioactive substance after t days is
A(t) = A*e^(-0.0025t) where A is the beginning amount.
How much do we need to begin with if we want 80 grams after 10 days?
:
write the equation:
A*e^(-0.0025t) = A(t)
Given values:
A(t) = 80
t = 10
Replace A(t) and t and we have:
A*e^(-0.0025*10) = 80
:
A*e^(-0.025) = 80
Find e^-.025 on a calc, then we have:
.97531A = 80
A =
A = 82.025 grams will decay to 80 grams in 10 days
;
:
Check this on a calc: enter: 82.025*e^(-.0025*10): results: 79.9998 ~ 80
:
How about this? Did we shed some light on this stuff for you?

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