Multiple choice

The mean of the marks in Statistics of 100 students in a class was 72 The mean of marks for boys was 75 while their number was 70 The mean of marks of girls in the class was

  1. $35$
  2. $65$
  3. $68$
  4. $86$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Total marks = 100 * 72 = 7200. Boys' marks = 70 * 75 = 5250. Girls' marks = 7200 - 5250 = 1950. Number of girls = 100 - 70 = 30. Mean for girls = 1950 / 30 = 65.

AI explanation

The total sum of marks for all 100 students is 100 times 72 equal to 7200. The total sum of marks for the 70 boys is 70 times 75 equal to 5250. The sum of marks for the girls is the total sum minus the sum of the boys marks, which is 7200 minus 5250 equal to 1950. Since there are 30 girls in the class, the mean mark for the girls is calculated by dividing 1950 by 30, giving 65.

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