The average marks of 100 students were found to be 40. Later on it was discovered that a score of 53 was misread as 83. Find the correct average corresponding to the correct score.
Options:
A . 39
B . 38.7
C . 41
D . 39.7
Answer: Option D Answer: (d)Total of correct marks = 100 × 40 – 83 + 53 = 3970 ∴ Correct average marks = $3970/100$ = 39.70 Aliter : Using Rule 26,If average of n numbers is m later on it was found that a number 'a’ was misread as 'b’. The correct average will be = m +${\text"(a-b)"}/ \text"n"$.Here, n = 100, m = 40 a = 53, b = 83 Correct Average = m +${\text"(a-b)"}/ \text"n"n$ = 40 +$({53-83}/100)$ = 40- $30/100$ = 39.70
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