Nuclear Decay question without knowing N0 or N ??

Bowenwww

1. The problem statement, all variables and given/known data
Ok so what I have an Am sample which emits alpha particles at a rate of 70Bq in 1997 and asks for the activity 8 years later (the half life of Am being 432.2 years) I found this to be 69.108 Bq, first of all does this sound right?


Secondly it asks for the number of nuclei both in 1997 AND 8 years later in 2005 - I have no idea to do this, is there an equation that relates the initial and final nuclei number without knowing either?


2. Relevant equations



3. The attempt at a solution

Dickfore

[tex]
A(t) = A_0 \, \exp(-\lambda \, t)
[/tex]

A is activity and is measured in bequerel ([itex]1 \, \mathrm{Bq} = 1 \, \mathrm{s}^{-1}[/itex])

daveb

Also, A(t) = λN(t)

Bowenwww

Yeah I sort of understand that it's just I don't know how to apply my answer for activity to find the nuclei number before and after

Dickfore

see post #3.