The first term of a geometric series is 20 and the common ratio is 0.9
Find the value of the fifth term.
Find the sum of the first 8 terms, giving your answer to one decimal place.
Given that \(S _ { \infty } - S _ { N } < 0.04\), where \(S _ { N }\) is the sum of the first \(N\) terms of this series, (c) show that \(0.9 ^ { N } < 0.0002\)