I got 6.49204 but you will need to round so D 6.5
I added all of the numbers up
Answer:
475.
Step-by-step explanation:
We have been given that for a normal distribution with μ=500 and σ=100. We are asked to find the minimum score that is necessary to be in the top 60% of the distribution.
We will use z-score formula and normal distribution table to solve our given problem.

Top 60% means greater than 40%.
Let us find z-score corresponding to normal score to 40% or 0.40.
Using normal distribution table, we got a z-score of
.
Upon substituting our given values in z-score formula, we will get:





Therefore, the minimum score necessary to be in the top 60% of the distribution is 475.
The chance of student 1's birthday being individual is 365/365 or 100%.
Then the chance of student 2's birthday being different is 364/365.
Then it's narrowed down to 363/365 for student 3 and so on until you get all 10 students.
If you multiply all these values together, the probability would come out at around 0.88305182223 or 0.88.
To get all the same birthday you'd have to the chance of one birthday, 1/365 and multiply this by itself 10 times. This will produce a very tiny number. In standard form this would be 2.3827x10'-26 or in normal terms: 0.23827109210000000000000000, so very small.
The last graph represents a system with no solutions. The solution to a system of equations is the point at which both lines intersect. Because the equations in the last graph don't intersect and are parallel, it has no solutions. Hope this helps :))