Original activity from total counts, short decay

[dirks555]

Homework Statement

I am supposed to calculate the original activity of a radioactive from the following data:

Total counts N
Measurement time t

Since the half-life is short compared to the measure time i can't just divide the counts with the time passed. I really have no clue on how to do this!

Homework Equations

A=A_0e^lambda*t

The Attempt at a Solution

 

[Ray Vickson]

Do you mean that at time t you know the total number of all decays up to t? What other information do you have?

RGV