Multiple choice

A pupil's marks were wrongly entered as 83 instead of 63. Due to that the average marks for the class got increased by half (1/2). The number of pupils in the class are:

  1. 10

  2. 20

  3. 40

  4. 73
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let n be the number of pupils. Increase in total marks = 83 - 63 = 20. Increase in average = 20 / n = 1/2. So n = 40.

AI explanation

Let the number of pupils be n. The total increase in the class's sum of marks is 83 minus 63, which is 20. Because this causes the average to increase by 1/2, we can write the equation n multiplied by 1/2 equals 20. Solving this gives n equals 40.

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