a classs if 25 students took a science test. 10 students had an average score of 80. the other students had an average score of 60. what is the average score of the whole class?
Answers
Total marks of 10 student with average 80 = 80x 10 = 800
total marks of 15 students with average 60 = 60 x 15 = 900
Average score of whole class = 800 + 900 = 1700/25 = 68
25
Given: A class of 25 students took a science test. 10 students had an average score of 80. The other students had an average score of 60.
To find: Average score of the whole class
Solution: Average is calculated by dividing the sum of observations by the number of observations.
In first case, 10 students had an average score of 80.
Here, average score = 80
Number of observations= Number of students= 10
Therefore,
Average score of these 10 students
= Sum of scores of these 10 students/10
=> 80 = Sum of scores of these 10 students/10
=> Sum of scores of these 10 students = 80 × 10
=> Sum of scores of these 10 students = 800
Now, the remaining students had average score of 60.
Remaining students
= Total students-10
= 25-10
= 15
Here, number of observations= 15
Therefore,
Average score of these 15 students= Sum of scores of these 15 students/15
=> Sum of scores of these 15 students = 60×15
=> Sum of scores of these 15 students=900
Total score of all 25 students
= 800+900
= 1700
Total number of observations (students)= 25
Average score of the class
= Sum of marks of all students/Total students
= 1700/25
= 68
Therefore, the average score of the class is 68.