The average of l0 items was found to be 80 but while calculating, one of the items was counted as 60 instead of 50. Then the correct average would have been :
Options:
A . 79.25
B . 69
C . 79.5
D . 79
Answer: Option D Answer: (d)Corrected mean = ${80 × 10 – 60 + 50}/10$= ${800 – 10}/10$ = $790/10$ = 79Aliter : Using Rule 26,The correct average will be = m +${\text"(a-b)"}/ \text"n"$. Here, n = 10, m = 80 a = 50, b = 60 Correct Average = m + ${\text"(a - b)"}/\text"n"$= 80+$ {(50- 60)}/10$= 80 – 1 = 79
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