Multiple choice

The average of marks for a class in science is 64 and the total number of students is 30. If the average of marks for girls is 78, and the number of boys is 18, what is the approximate average of marks scored by the boys?

  1. 55

  2. 60

  3. 64

  4. 72

  5. 74
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A Correct answer
Explanation

Total students = 30. Girls = 30 - 18 = 12. Total marks = 30 * 64 = 1920. Girls' total = 12 * 78 = 936. Boys' total = 1920 - 936 = 984. Boys' average = 984 / 18 = 54.66, which is approximately 55.

AI explanation

Using the weighted average method, the sum of the marks for all 30 students is 30 multiplied by 64, giving 1920. Since there are 18 boys, the number of girls is 12, making the girls' total marks 12 multiplied by 78, which is 936. The total marks for the boys is the overall total minus the girls' total, so 1920 minus 936 equals 984. Dividing the boys' total of 984 by the 18 boys gives an approximate average of 55.

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