Answer:
The correct option is b. approximately 68% of the data falls within 1 standard deviation (+-1) of the mean
Explanation:
According to the empirical rule of normal distribution:
1. Approximately 68% of the data falls within 1 standard deviation 
of the mean
2. Approximately 95% of the data falls within 2 standard deviations 
of the mean
3. Approximately 99.7% of the data falls within 3 standard deviations 
of the mean.
Therefore, among the given options, only option b adheres to the empirical rule of the normal distribution. Therefore, the option b is correct
Answer: Jiří is 5 years old.
Step by step:
Let x denote Jiří's age in years. Then Pamela's age is 3x. Their sum is x + 3x = 20. So we solve for x:
x + 3x = 20
4x = 20
x = 5
Jiří's age is 5 years
Answer:
since numerator does not change for this equation, just put x+5=30 which is 25
Step-by-step explanation:
It would also have a slope of 3/5 because parallel lines are lines with the same slope.
It may help you to consider the standard normal curve. If the mean here is 70%, then 0.5 of the area under this curve. In other words, half the students received a grade > 70%. That would be 100 students.
Note that 84 is 2 std dev above the mean.
Recall the Empirical Rule: 95% of scores lie within 2 std. dev of the mean.
Measuring from the mean, that would be 47.5% above the mean and 47.5% below the mean. The area to the right of the mean is 0.5. Subtract 0.475 from that to obtain the fraction of students who rec'd a grade greater than 2 std dev from the mean: It's 0.025.
Then the # of students who rec'd a grade greater than 84% would be
0.025(200 students) = 5 students.
