[" The weighted mean of first "n" natural numbers whose weights are equal to the squares of corre "],[" The weighted mean of first "n" natural numbers whose weights are equal to the squares of corre "],[" numbers is "(a)(n+1)/(2)," (b) "(3n(n+1))/(2(2n+1))quad " (c) "((n+1)(2n+1))/(6)" (d) "(n(n+1))/(2)]