Quandaries and Queries


The first three terms of a geometric series are 3(q+5), 3(q+3), (q+7) respectively.
Calulate the value of q.

Thankyou very much!




The distinguishing feature of a geometric sequence is the common ratio, often designated r. The defining property is that if s and t are two successive terms in the sequence then

t = r s.

Thus the second term is r times the first term, and the third term is r times the second term. Hence for your sequence

3(q + 3) = r 3(q + 5)


(q + 7) = r 3(q + 3)

From the first equation

r = (q + 3)/(q + 5)

and from the second equation

r = (q + 7)/3(q + 3)


 (q + 3)/(q + 5) =  (q + 7)/3(q + 3)

Solve for q.



Go to Math Central