There is a probability of 77% that the mean of this sample is between 19.25 hours and 21.0 hours
Z score is used to determine by how many standard deviations the raw score is above or below the mean. The z score is given by:

Given that μ = 20, σ = 7, n = 125.
For x = 19.25:

From the normal distribution table, P(-1.20 < z < 0.62) = P(z < 0.62) - P(z < -1.2) = 0.8849 - 0.1151 = 0.7698 = 77%
There is a probability of 77% that the mean of this sample is between 19.25 hours and 21.0 hours
Find out more on z score at: brainly.com/question/25638875
Answer:
Choices C and D
Step-by-step explanation:
The most simplest way is just to solve each one and see which two have the same answer as the first expression.
But you could also see that both of the
are going to cancel each other out so you are left with
which is also choice C.
For choice D I distributed the negative one to the insides of the parenthesis that left me with
which is the same expression as the first one.
Answer:
The twins would be 13 years old.
Step-by-step explanation:
21+21+21+13+13 = 89