Multiple choice

The average marks of 10 students in an examination were 25. It was later found that the marks of 1 student had been wrongly entered as 34, instead of 43. What is the correct average?

  1. 25.5

  2. 24.1

  3. 24.5

  4. 25.9
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D Correct answer
Explanation

The initial sum of marks was 10 * 25 = 250. The error was subtracting 34 instead of adding 43, so the difference is 43 - 34 = 9. The new sum is 250 + 9 = 259, and the new average is 259 / 10 = 25.9.

AI explanation

Using the formula Sum = Average x Count, the initial total marks are 10 x 25 = 250. The marks of one student were wrongly entered as 34 instead of 43, meaning the total sum needs to be increased by 9, making the correct sum 259. The correct average is the correct sum divided by the number of students, which is 259 / 10 = 25.9.

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