We are given that 1a1,1a2,1a3,.....1an are in A.P.
∴∑ana1,∑ana2,∑ana3,..... are alos in A.P.
or1+a2+a3+....+ana1,1+a1+a3+....+ana2,..... are in A. P.
a2+a3+....+ana1,a1+a3+....+ana2,..... are in A.P.
Take their reciprocal and hence given numbers are in H.P.