Multiple choice

In an exam, the average marks of 62 students were found to be 54, but marks of a student were counted as 57, instead of 75, by mistake. Find the correct average.

  1. 54.29

  2. 55.00

  3. 64.29

  4. 64.00

  5. None of these
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A Correct answer
Explanation

Original sum = 62 * 54 = 3348. Error: 57 was added instead of 75. Correct sum = 3348 - 57 + 75 = 3366. Correct average = 3366 / 62 = 54.29.

AI explanation

The correct sum should increase by the difference between 75 and 57, which is an addition of 18. Divide this increase of 18 by the total number of 62 students to find the required adjustment to the mean. The result is 0.2903. Add this value to the initial average of 54 to find the accurate mean. The correct average is 54.29.

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