Answer:
0.97725
Step-by-step explanation:
Given that Professor Heinz has given the same multiple-choice final exam in his Principles of Microeconomics class for many years. After examining his records from the past 10 years, he finds that the scores have a mean of 76 and a standard deviation of 12.
i.e.
Std error of mean = sigma/sqrt n = 2
Thus the sample mean is N(76,2)
Required probability = probability that a class of 36 students will have an average greater than 72 on Professor Heinz's final exam.
=
Answer:
y = (x + 4)(x - 9)
Step-by-step explanation:
x = {-4, 9}
y = (x + 4)(x - 9)
X=number of boys.
y=number of girls.
we suggest this system of equation
x/y=9/7
x=y+116
We solve this system of equation by substitution method.
(y+116)/y=9/7
7(y+116)=9y
7y+812=9y
9y-7y=812
2y=812
y=812/2=406
x=y+116
x=406+116=522
answer: At the school there are 522 boys and 406 girls.
to chek.
522/406=1.2857...
9/7=1.2857...
The number of boys (522) is equal to 406+116=522.