30 students in a class appeared in an examination. The average marks of 12 students is 62, and the average marks of the remaining 18 students is 68. What is the average marks of the entire class?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 65.6.
Short method:
12 → 62
18 → 68
Average of the class = 62 + () = 62 + 3.6 = 65.6
Alternate method:
The total score of 12 students = 12 × 62 = 744
The total score of 18 students = 18 × 68 = 1224
Average score = (744 + 1224)/30 = 1968/30 = 65.6