If a,1b,c and 1p,q,1r form two arithmetic progressions of the same common difference, then a, q, c are in A.P. if
p, b, r are in A.P.
1p,1b,1r areinA.P.
p, b, r are in G.P
none of these
Since a, q and c are in A.P., so2q=a+c⇒1p+1r=2b⇒1p,1b,1r are in A.P.