Multiple choice

The average of marks of 65 students in a class was calculated as 150. It was later realised that the marks of one of the students were calculated as 142, whereas his actual marks were 152. What is the actual average of marks of the group of 65 students? (Rounded off to two digits after decimal)

  1. 151.25

  2. 150.15

  3. 151.10

  4. 150.19

  5. None of these
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B Correct answer
AI explanation

The correct total marks increase by the difference between the actual marks and the incorrectly calculated marks, which is 152 minus 142, resulting in an increase of 10 marks. Using the shortcut for average correction, the actual average is the old average plus the correction divided by the total number of students. This calculates to 150 plus 10 divided by 65, which equals 150 plus 0.1538, resulting in an actual average of 150.15.

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