the answer is 200
step-by-step explanation:
this is a problem about poisson probabilities. i don't know if you've
already studied poisson distributions, or if you have a place to look
to read more about the subject.
here's how you can see a poisson distribution coming. when there are
a lot of events that may happen at any time (or any place), and when
you're counting how many of them happen at a particular time (or a
particular place), and each event is independent of the others, then
the result is a poisson distribution. this is roughly true for the
chocolate chips; one chip being in a cookie has only a small effect on
the probability that another chip will be in the cookie.
once you know you have a poisson distribution, you know a lot. there
is only one parameter to a poisson distribution, so if you know the
mean, you know everything. the form of the distribution is
probability of n chips = {[e^(-x)]*(x^n)} / (n! )
