The average of 20 numbers is calculated as 35. It is dicovered later, that while calculating the average, one number, namely 85, was read as 45. The correct average is
Options:
A . 37
B . 36.5
C . 36
D . 37.5
Answer: Option A Answer: (a)Correct sum of 20 numbers = 20 × 35 – 45 + 85 = 700 + 40 = 740 ∴ Correct average = $740/20$ = 37 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 = 20, m = 35 a = 85, b = 45 Correct mean = m + ${\text"(a - b)"}/\text"n"$ = 35 +${(85 - 45)}/20$ = 35 + 2 = 37
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