Three groups of students have average marks 50, 60, and 70 respectively. The number of students in these groups are 20, 30, and 50. What is the combined average of all students?
Show answer & explanation
Correct answer: A
Explanation
Average₁ = 50, Students = 20
Average₂ = 60, Students = 30
Average₃ = 70, Students = 50
Sum of the first group = 50 × 20 = 1000
Sum of the second group = 60 × 30 = 1800
Sum of the third group = 70 × 50 = 3500
Total Sum = 1000 + 1800 + 3500 = 6300
Total Students = 20 + 30 + 50 = 100
Combined Average = 6300 / 100 = 63