Question

Calculate the partial sum S(5) for the sequence 243, 81, 27,... .

Answer 1

$s(5) = \frac{243(1 - ( { \frac{1}{3})^{5} )} }{1 - \frac{1}{3} } = \frac{242}{ \frac{2}{3} } = 3 \times 121 = 363$