The average score of all the students in both classes is 84.
<h3>How to calculate the average?</h3>
The class with 30 students had an average score of 80 on a test. The total score will be:
= 30 × 80
= 2400
A class with 20 students had an average score of 90 on the same test. The total score will be:
= 20 × 90
= 1800
Total scores = 2400 + 1800 = 4200
Number of students = 20 + 30 = 50
The average score will be:
= Total score / Total students
= 4200 / 50
= 84
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Answer: Therefore it must be the first one, 40
Step-by-step explanation: Vertical angles are always congruent, which means that they are equal. x = 40
Answer: a) 
b) 
c) 
Step-by-step explanation:
Given : Number of students : 11
Number of faculty members : 13
Total persons : 
Total number of ways to structure a jury of six people from a group of 24 people :-

a) Number of ways of selecting a jury of all students :-

Then , the probability of selecting a jury of all students :-

b) Number of ways of selecting a jury of all faculty :-

Then , the probability of selecting a jury of all students :-

c) Number of ways of selecting a jury of two students and four faculty :-

Then , the probability of selecting a jury of all students :-
