Question

if the two terms of a gemotric sequence are a1=216, and a2=72, which is the third term? a3?

Answer 1

$GEOMETRIC \: \: PROGRESSIONS \\ \\ \\ Let \: the \: G.P. \: be \: \: A \: , \: Ar \: , \: A {r}^{2} \: ... \\ \\ Where \:first \: term \: is \: \: A \: \: \\ and \: common \: ratio \: is \: \: R \\ \\ Let \: An \: denotes \: the \: \: nth \: term \: of \: \\ the \: given \: Geometric \: Progression \: \\ \\ It \: is \: given \: - \\ \\ A1 \: = \: 72 \\ \\ A2 \: = \: 216 \\ \\ Common \: ratio \: = \: \frac{A2}{A1} = \frac{216}{72} \\ \\ R = 3 \\ \\ A \: = \: 72 \\ \\ A3 \: = \: A {r}^{2} = 72 \times 3 \times 3 \\ \\ \\ Hence \: , \: A3 \: = \: 648 \: \: \: \: \: \: \: Ans.$