Going against the current, a boat takes 6 hours to make a 120-mile trip. when the boat travels with the current on the return trip, it takes 5 hours.

what is the rate of the boat in still water?

a) 2 mph
b) 20 mph
c) 22 mph

5(x+y)=6(x-y)=120

x+y=24

x-y=20

x=22

y=2

 Hope this helps! :)

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! )