## Nuclear Decay question without knowing N0 or N ??

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
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 $$A(t) = A_0 \, \exp(-\lambda \, t)$$ A is activity and is measured in bequerel ($1 \, \mathrm{Bq} = 1 \, \mathrm{s}^{-1}$)
 Also, A(t) = λN(t)

## Nuclear Decay question without knowing N0 or N ??

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
 see post #3.

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