Answer:
Class average is 83.6
Step-by-step explanation:
We are given the following information in the question:
Twelve of the members had an average score of 80. Eighteen of the members had an average score of 86.
Total number of students = 12 + 18 = 30
Formula:
[tex]Mean = \displaystyle\frac{\text{Sum of all marks}}{\text{Total number of students}}[/tex]
[tex]Mean = \displaystyle\frac{\text{Sum of all marks of 12 students}}{\text{Total number of students}} \\\\\Rightarrow 80 = \displaystyle\frac{\text{Sum of all marks of 12 students}}{12}\\\\\Rightarrow \text{Sum of all marks of 12 students} = 960[/tex]
[tex]Mean = \displaystyle\frac{\text{Sum of all marks of 18 students}}{\text{Total number of students}} \\\\\Rightarrow 86 = \displaystyle\frac{\text{Sum of all marks of 12 students}}{18}\\\\\Rightarrow \text{Sum of all marks of 18 students} = 1548[/tex]
Class average =
[tex]\text{Mean} = \displaystyle\frac{\text{Sum of all marks of all students}}{\text{Total number of students}} \\\\ = \displaystyle\frac{960+1548}{12} = \displaystyle\frac{2508}{12} = 83.6[/tex]
Class average is 83.6
