Multiple choice

Marks of a student were entered as 95 in place of 80 by mistake. According to this, the average marks for the class increased by half. How many students were there in the class?

  1. 15

  2. 20

  3. 30

  4. 40

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Difference in marks = 95 - 80 = 15. This total difference caused an average increase of 0.5. Let n be the number of students: 15 / n = 0.5, so n = 30.

AI explanation

Using the average formula, the difference between the correct marks and the incorrect marks is the total increase in marks for the class, so 95 - 80 = 15. This 15 point increase is distributed equally among all students to raise the average by 0.5, so the number of students is 15 / 0.5. The calculation gives 30 as the number of students in the class.

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