Multiple choice

There are 100 students in a class. 40 of them are girls. The average mark of the boys in science is 75% and that of the girls is 65%. Find the average marks of the class in science.

  1. 81%

  2. 51%

  3. 61%

  4. 71%
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D Correct answer
Explanation

Boys = 60, Girls = 40. Average marks = (60 * 75 + 40 * 65) / 100 = (4500 + 2600) / 100 = 7100 / 100 = 71%.

AI explanation

Using the weighted average formula, multiply each subgroup average by its respective size and divide by the total number of students. The total marks for the 60 boys is 60 multiplied by 75, which equals 4500, and the total marks for the 40 girls is 40 multiplied by 65, which equals 2600. The sum of all marks is 4500 plus 2600, equaling 7100. Divide this total by the 100 students to get an overall class average of 71%.

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