Multiple choice

The average of marks of $12$ students is $15$. The marks of a student who scored zero were wrongly taken as $18$ and average was determined. The correct average marks is _________.

  1. $15$
  2. $14.5$
  3. $13.5$
  4. $12$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The initial sum of marks was 12 * 15 = 180. Since 18 was incorrectly added instead of 0, the correct sum is 180 - 18 = 162. The correct average is 162 / 12 = 13.5.

AI explanation

The total marks of the 12 students is 12 multiplied by 15, which equals 180. The correct score is zero, so the sum must be reduced by the wrongly added 18 marks, making the correct sum 162. Dividing 162 by 12 students gives the correct average of 13.5.

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