A class of 30 students appeared in a test. The average score of 12 students is 80 and that of the rest is 75. What is the average score of the class?

Correct option is C

Given:
Average score of 12 students = 80.
Average score of remaining 18 students = 75.
Formula Used:
​$$\text{Average score of the class} = \frac{\text{Total score of all students}}{\text{Number of students}}.$$​​
Solution:
Total score of 12 students = 12 \times 80 = 960
Total score of 18 students = 18 \times 75 = 1350
Total score = 960 + 1350 = 2310
Average score =$$\frac{2310}{30}$$​ = 77.
​$$\text{The average score of the class is 77.}$$​​