The average marks obtained by a student in 6 subjects is 88. On subsequent verification it was found that the marks obtained by him in a subject was wrongly copied as 86 instead of 68. The correct average of the marks obtained by him is
Options:
A . 85
B . 87
C . 86
D . 84
Answer: Option A Answer: (a)Correct sum of marks obtained by the student = 88 × 6 – 86 + 68 = 528 – 86 + 68 = 510∴ Correct average = $510/6$ = 85 Aliter : Using Rule 26, The correct average will be = m +${\text"(a-b)"}/ \text"n"$.Here, n = 6, m = 88 a = 68, b = 86 Correct mean = m + ${\text"(a - b)"}/\text"n"$= 88 +${(68 - 86)}/6$= 88 - $18/6$ = 85
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