**1. The problem statement, all variables and given/known data**

The average counting rate of a radioactive sample is 486 cpm (counts per minute). Find the probability that in any given 10s interval one gets less than 72 counts. Is this the same as the probability of getting less than 72 X 6 = 432 counts in 60s?

**2. Relevant equations**

**3. The attempt at a solution**

I’m not really sure where to start. I do not think that the probability of less than 72 counts in 10s is the same as getting less than 72 x 6 counts in 60s though.

http://ift.tt/1ic8oDR