We first find the class mark xi, of each class and then proceed as follows
Weight~(in~kg) Number~of~wrestlers(fi)Class~marks(xi)Deviations di=xi−afidi100−1104105−20−80110−12014115−10−140120−13021a=12500130−14081351080140−15031452060N=∑fi=50∑fidi=−80
∴ Assumed mean (a) = 125,
Class width (h) = 10 and total observation (N) = 50
By assumed mean method,
Mean (¯x)=a+∑fidi∑fi
=125+(−80)50
=125−1.6=123.4kg