. If the sum of deviations of a number of observations about 4 is 30 and that about 3 is 40. Then, mean of the observations is

Given that,∑i=1n xi−4=30and   ∑i=1n xi−3=40i.e..,Σxi−4n=30     (i)and Σxi−3n=40        ..(ii)On solving Eqs. (i) and (ii), we getn=10 and Σxi=70∴∑i=1n xi   Mean =110(70)=7