In a G.P., the first term is 7 and the last term is 448. If the sum of the terms is 889, find the common ratio.
Answer: A
We use the formula for the sum of a G.P.: \(S_n = \frac{lr-a}{r-1}\), where l is the last term. Given \(S_n=889, l=448, a=7\). \(889 = \frac{448r-7}{r-1} \Rightarrow 889(r-1) = 448r-7 \Rightarrow 889r - 889 = 448r - 7 \Rightarrow 441r = 882 \Rightarrow r = 882/441 = 2\).