Let a,b and c be in G.P. with common ratio r , where and
. If 3a , 7b and 15c are the first three terms of an A.P.,
then the 4th term of this A.P. is :
Since a,b,c are in G.P. with common ratio r
b = ar ,
Also 3a, 7b and 15c are in A.P.
So, terms are
So, 4th term
So, option (4) is correct.
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