Answer:
1/4 < 5/4
Step-by-step explanation:
Since the numbers have the same denominator, we compare the numerators
1<5
so 1/4 < 5/4
Answer:
Where
and 
Since the distribution for X is normal then the distribution for the sample mean is also normal and given by:



So then is appropiate use the normal distribution to find the probabilities for 
Step-by-step explanation:
Previous concepts
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean". The letter
is used to denote the cumulative area for a b quantile on the normal standard distribution, or in other words: 
Solution to the problem
Let X the random variable that represent the variable of interest of a population, and for this case we know the distribution for X is given by:
Where
and 
Since the distribution for X is normal then the distribution for the sample mean
is also normal and given by:



So then is appropiate use the normal distribution to find the probabilities for 
Answer:
84
Step-by-step explanation:
x = number of girls
The total for boys is 2x * 81 and for girls it would be 90x
Therefore, the equation goes like this:
2x * 81 + 90x
Then simplify, and set to equal 3x...
3x = 252
Which is the same as
x = 84
Thank me later :)
Answer:
Step-by-step explanation:
The letter A has at least 1 line of symmetry
Answer:
Step-by-step explanation:
Let μ - mean, σ - standard deviation.
<h3>Given:</h3>
A score of 30 falls three standard deviations below the mean:
A score of 60 falls three standard deviations above the mean:
Add up the two expressions and find the value of μ:
- μ - 3σ + μ + 3σ = 30 + 60
- 2μ = 90
- μ = 45
The mean is 45