MathematicsHard178×since 2002Q5198Let 1x1,1x2,...,1xn {1 \over {{x_1}}},{1 \over {{x_2}}},...,{1 \over {{x_n}}}\,\,x11,x21,...,xn1 (x_i ≠\ne= 0 for i = 1, 2, ..., n) be in A.P. such that x₁=4 and x₂₁ = 20. If n is the least positive integer for which xn>50,{x_n} > 50,xn>50, then ∑i=1n(1xi)\sum\limits_{i = 1}^n {\left( {{1 \over {{x_i}}}} \right)}i=1∑n(xi1) is equal to :A18{1 \over 8}81B3C138{{13} \over 8}813D134{{13} \over 4}413Check answerSkip