The average weight of a group of 20 boys was calculated

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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

1. 88.95 kg
2. 89.25 kg
3. 89.55 kg
4. 89.85 kg

Correct Option: D

According to question ,
Difference in weight = 87 – 78 = 9 kg

∴ Correct average weight = 89.4 +	9
	20

Correct average weight = 89.4 + 0.45 = 89.85 kg
Second method to solve this question with the help of given formula :
Here, n = 20, m = 89.4 a = 87, b = 78

Correct Average = m +	(a -b)
	n

Correct Average = 89.4 +	(87 - 78)
	20

Correct Average = 89.4 +	9
	20

Correct Average = 89.4 + 0.45 = 89.85 kg