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.
Answer:
Samsung S10
Step-by-step explanation:
Price Plans
iPhone 11 Pro: $41.67/mo.
Galaxy S10: $31.25/Mo
<u>_________________</u>
Why?
<em>The Galaxy S10 has a 6.1-inch screen that's slightly larger than the iPhone 11 Pro's 5.8-inch display. It's also sharper than Apple's iPhone, or at least it should be on paper. ... But having a higher resolution doesn't always mean one screen is better than the other.</em>
Answer: Let length = 2x + 3
Let width = x
Area = 54 ft2
length × width = Area
x(2x + 3) = 54
2x2 + 3x = 54
2x2 + 3x - 54 = 0
(2x - 9)(x + 6) = 0
x = 9/2 and x = -6
x = 4.5 and x = -6
We accept x = 4.5 because length cannot be a negative value. Substituting this value into the dimensions:
width = 4.5 ft
length = 2(4.5) + 3 = 9 + 3 = 12 ft
Step-by-step explanation:
If we are scaling up the surface area by a factor of 10 means that the two dimensions of area are each being increased by 10 times the original size. Therefore, the surface area is increased by a factor of 10 x 10, or by a factor of 100.