- In this question you must show detailed reasoning.
Solutions relying entirely on calculator technology or numerical methods are not acceptable.
A geometric sequence has first term \(a\) and common ratio \(r\), where \(r > 0\)
Given that
- the 3rd term is 20
- the 5th term is 12.8
- show that \(r = 0.8\)
- Hence find the value of \(a\).
Given that the sum of the first \(n\) terms of this sequence is greater than 156
find the smallest possible value of \(n\).