Each number is mutliplied by 3 and then numbers 2,3,4,5,... are added successively.
2*3+2=8
8*3+3=27
27*3+4=85
85*3+5=260
260*3+6=786
So it's 786.
Btw, the general formula for this sequence is 
So to find the mean you add up all the numbers (or the exam scores) which will get you 212 then you take the number and divide it by the total numbers in the set (how many numbers did you add up?)
212 divided by 8 is 26.5 which would be C. I hope this helps!
Answer:
20,30
Step-by-step explanation:
multiply by the factor for each one to get a bigger picture
Calculate the value of z and its probability, since with this we can know how likely it is that this will happen.
We have that the mean (m) is equal to 8.3, the standard deviation (sd) 1.2 and the sample size (n) = 15
They ask us for P (x =7.2)
For this, the first thing is to calculate z, which is given by the following equation:
z = (x - m) / (sd / (n ^ 1/2))
We have all these values, replacing we have:
z = (7.2 - 8.3) / (1.2 / (15 ^ (1/2))
z = -3.55
With the normal distribution table (attached), we have that at that value the approximate probability is:
P (z = -3.55) = 0.0001
The probability is 0.01 %
This affirms that the students do not sleep what the study says because the probability of this happening according to the survey is almost nil.