After a power failure, the temperature in a freezer increased at an average rate of 3.5 °F per hour. The total increase was 10.5 °F. Enter and solve an equation to find the number of hours until the power was
restored. Let x represent the number of hours it takes for the temperature to increase to 10.5 °F.

x=hours

7.5=2.5x

3=x

x=3

3 hours until the power was restored

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! )