A geometric series has first term 5 and common ratio 45\displaystyle \frac{4}{5}54.
Calculate
the 20th term of the series, to 3 decimal places,
the sum to infinity of the series.
Given that the sum to k k\,k terms of the series is greater than 24.95, show that k>log0.002log0.8\displaystyle k > \frac{\log 0.002}{\log 0.8}k>log0.8log0.002,
find the smallest possible value of kkk.
Practise Edexcel A Level Old Maths Sequences and Series with exam-style questions for A Level Old Maths. 10 questions, matched to the Edexcel A Level Old Maths (9371) specification and written in Unit exams C1, C2, C3 and C4 plus two applied units (e.g. S1 and M1) style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.