The average weight of a group of 20 boys was calculated to be 89.4 kg and it was later discovered that one weight was misread as 78 kg. instead of 87kg. The correct average weight is
Options:
A . 89.25 kg
B . 88.95 kg
C . 89.85 kg
D . 89.55 kg
Answer: Option C Answer: (c)Difference in weight = 87 – 78 = 9 kg ∴ Correct average weight = 89.4 + $9/20$= 89.4 + 0.45 = 89.85 kg 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 = 89.4 a = 87, b = 78 Correct Average = m + ${\text"(a-b)"}/ \text"n"n$ = 89.4+${(87-78)}/20$= 89.4 + $9/20$= 89.4 + 0.45 = 89.85 kg
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