Calculating Probability with Poisson Distribution: Radioactive Source Counts

[Silviu]

Hello! I came across this problem: A counter near a long-lived radioactive source measures an average of 100 counts per minute. What is the probability that more than 110 counts will be recorded in a given one-minute interval? I am not sure how to do it. Applying the Poisson distribution formula involves very big numbers.

 

[Orodruin]

Hint: 100 is a fairly large number.

 

[Silviu]

Hint: 100 is a fairly large number.

I am not sure how to use that...

 

[MarneMath]

Central limit theorem comes to mind. Also being aware that the mean and variance are equal in a Poisson is useful too.

 

[WWGD]

I am not sure how to use that...

http://thomaswhitham.pbworks.com/f/6.Po+to+norm.pdf