Multiple choice

The average marks of a class of 35 children is 35. The marks of one of the students, who got 35, was incorrectly entered as 65. What is the correct average of the class?

  1. 33.76

  2. 34.14

  3. 35.24

  4. 36.50
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B Correct answer
Explanation

The initial total marks were 35 * 35 = 1225. The error was adding 65 instead of 35, so the difference is 30. Subtracting 30 from the total gives 1195. The new average is 1195 / 35 = 34.14.

AI explanation

Using the average formula, the total decrease in marks is 65 - 35 = 30. Dividing this difference by the total number of students gives the decrease in the average: 30 divided by 35 equals 0.857. Subtracting this from the initial average yields 35 - 0.857 = 34.14, which is the correct average.

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