A chemical reaction is monitored at regular time intervals, and the concentration of the remaining catalyst, CCC, is found to follow a geometric progression with first term aaa and common ratio rrr, where r>0r > 0r>0.
Given that:
Show that r=23r = \frac{2}{3}r=32.
Determine the value of aaa.
Given that the sum of the concentrations recorded over the first nnn intervals is greater than 242.5 mg/L
Find the smallest possible value of nnn.
(Solutions based entirely on graphical or numerical methods are not acceptable.)
Practise AQA A Level Maths 1.7 D: Sequences and series with exam-style questions for A Level Maths. 267 questions covering 1.7.1 Binomial expansion, 1.7.2 Types of sequence (A-level only), 1.7.3 Sigma notation (A-level only), 1.7.4 Arithmetic sequences and series (A-level only), 1.7.5 Geometric sequences and series (A-level only), and 1.7.6 Sequences and series in modelling (A-level only), matched to the AQA A Level Maths (7357) specification and written in Paper 1, Paper 2 and Paper 3 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.
