Multiple choice

The average marks of 3 classes of 60, 55 and 45 students are 50, 60 and 55, respectively. Find the average marks of all the students.

  1. 53.33

  2. 54.84

  3. 55

  4. 56

  5. 57
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B Correct answer
Explanation

Total marks = (60 * 50) + (55 * 60) + (45 * 55) = 3000 + 3300 + 2475 = 8775. Total students = 60 + 55 + 45 = 160. Average = 8775 / 160 = 54.84375.

AI explanation

Using the weighted average formula, the overall average is the sum of the products of the number of students and their respective averages divided by the total number of students. The total marks are (60 times 50) plus (55 times 60) plus (45 times 55), giving 3000 plus 3300 plus 2475, which equals 8775. The total number of students is 60 plus 55 plus 45, which is 160. Dividing 8775 by 160 gives the average marks of 54.84.

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