Question
Mean of 10 numbers is 30. Later on it was observed that numbers 15, 23 are wrongly taken as 51, 32. The correct mean is
Answer: Option B Answer: (b)Difference = 15 + 23 – 51 – 32 = –45∴ Correct average = 30 -$45/10$ = 25.5Aliter : Using Rule 27, The correct average = m +${\text"(a+b-p-q)"}/ \text"n"$. Here, n = 10, m = 30 a = 15, b = 23 p = 51, q = 32 Correct Average = m + ${\text"(a + b - p - q)"}/ \text"n"n$ = 30 + ${(15 + 23 - 51 – 32)}/10$= 30 + $({38-83}/10)$= 30 - $45/10$= 30 – 4.5 = 25.5
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