Answer:
The mean is 11.5 minutes and the standard deviation is of 6.64 minutes
Step-by-step explanation:
An uniform probability is a case of probability in which each outcome is equally as likely.
For this situation, we have a lower limit of the distribution that we call a and an upper limit that we call b.
The mean is:

The standard deviation is:

Arrival time of 9:18 am and a late arrival time of 9:41 am.
9:41 is 23 minutes from 9:18. So the time is uniformily distributed between 0 and 23 minutes, so a = 0, b = 23.
Mean:

Standard deviation:

The mean is 11.5 minutes and the standard deviation is of 6.64 minutes
Answer:
Pr(X >42) = Pr( Z > -2.344)
= Pr( Z< 2.344) = 0.9905
Step-by-step explanation:
The scenario presented can be modeled by a binomial model;
The probability of success is, p = 0.65
There are n = 80 independent trials
Let X denote the number of drivers that wear a seat belt, then we are to find the probability that X is greater than 42;
Pr(X > 42)
In this case we can use the normal approximation to the binomial model;
mu = n*p = 80(0.65) = 52
sigma^2 = n*p*(1-p) = 18.2
Pr(X >42) = Pr( Z > -2.344)
= Pr( Z< 2.344) = 0.9905
8 x ¾ is the same as adding ¾ + ¾ + ¾ + ¾ + ¾
because, when you are adding 3/4
8 times, you are 3/4 plus itself,
eight times,
so you are doing 3/4*8
3x - 15 = 105
3x = 120
x = 40
3(40) - 15 + y + 24 = 180
120 - 15 + y + 24 = 180
129 + y = 180
y = 51