Answer:
yes
Step-by-step explanation:
Answer:

And we can find this probability using the normal standard table or excel and we got:

The figure shows the calculation for this case.
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".
Solution to the problem
Let X the random variable that represent the hardness of a population, and for this case we know the distribution for X is given by:
Where
and 
We are interested on this probability

And the best way to solve this problem is using the normal standard distribution and the z score given by:

If we apply this formula to our probability we got this:

And we can find this probability using the normal standard table or excel and we got:

The figure shows the calculation for this case.
First, you multiply 2/5 by -5 to get -2. Then, you multiply -2 by -2/3 (-4/6's simplified form) to get 1 1/3 as your answer.
Answer:
$3.25 per gallon
Step-by-step explanation:
She had $30 and now has $4, so she spent $30- $4 = $26
With $24 she bought 8 gallons of gas.
$26/(8 gallons) = $3.25/(1 gallon) [ divide 26 by 8 to get the unit rate]
She spent $3.25 per gallon
Answer:
A, B, E, and F
Step-by-step explanation:
sinx and cosx are defined for all values of x. So, sin⁻¹x and cos⁻¹x are also defined for all values of x.
A and E are correct.
tanx is defined for all values of x.
However, tan(nπ) = 0 at when n is an integer. So, tan⁻¹(±nx) is undefined. However, tan⁻¹(-½x) is defined, because -½ is not an integer.
B and F are correct.
C and D are <em>wrong</em>. Both sec⁻¹x and csc⁻¹x are undefined when -1 < x < 1, and -½ is in this forbidden region.