# How to solve this example using Poisson Distribution?

Particles are suspended in a liquid medium at a concentration of 4 particles per mL. A large amount of the suspension is thoroughly agitated, and then 3 mL are withdrawn . Let $X$ be the number of the particles in the 3 mL. Answer the following:

a- The distribution of X is a Poisson distribution, what is its parameter ($\lambda$)?

b- Find the probability that no particle is withdrawn from the 3 mL.

c- Find the probability that one particle is withdrawn from the 3 mL.

• I solved "a" as following but I do not know if it right or not : if there are 4 particles in 1 ml then there are 12 particles in 3 ml . but in this case should I consider the value 12 lambda ? – Psycho 4 Physics Jun 3 '13 at 5:06
• Please add the self-study tag and read the tag info. What do you know about Poisson distributions? – Glen_b -Reinstate Monica Jun 3 '13 at 5:55

a) Yes, you're correct, the value of $\lambda$ should be 12.