Pre-orders for the year cost $38 eac, while full pricce costs $45 each. if 24 students in mr. hillmans homeroom purchased yearbooks for a total of $975, how many students pre-ordered and how many bought their yearbook at full price ?

15  students pre-ordered and 9  students bought their yearbook at full price.

Step-by-step explanation:

Let x be the number of students pre-ordered \and y be the number of students  bought their yearbook at full price .

As per given , we have

Pre-orders for the year cost $38 each, while full price costs $45 each.

If 24 students in Mr.Hillmans homeroom purchased yearbooks for a total of $975.

i.e.  ...(i)

 ...(ii)

Multiplying equation (i) by 38 , we get

 ...(iii)

Subtracting (iii) from (ii) , we get

Put value of y in (i) , we get

Hence, 15  students pre-ordered and 9  students bought their yearbook at full price.

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! )