We start to solve this by looking for the formula that let us calculate an average value, this formula would be:

where Save is the average score and s is the score of each exam, Since we know the value of the score Save and 4 of the exams we can replace them in the formula, like this:
And we can solve for s5, which is the score that we need to find, like this:

Then, Pedro must have a 55 score on the fifth test
36, because 6^4 /6^2 is 6^2 and 6*6 (6^2) is 36
Answer: 0.6065
Step-by-step explanation:
Given : The machine's output is normally distributed with


Let x be the random variable that represents the output of machine .
z-score : 
For x= 21 ounces

For x= 28 ounces

Using the standard normal distribution table , we have
The p-value : 

Hence, the probability of filling a cup between 21 and 28 ounces= 0.6065