3.21 meters
There's 100 centimeters in a meter (centi means 100) so 79 centimeters equals 0.79 meters. So 4 - 0.79 is 3.21
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:
75%
Step-by-step explanation:
It's right
Answer: The required probability is 
Step-by-step explanation:
Since we have given that
Number of people came into Brad's store = 48
Number of them made a purchase = 40
So, the experimental probability that the next person to come into the store will make a purchase would be

Hence, the required probability is 