An arithmetic sequence has first term a a\,a and common difference ddd. The sum of the first 8 terms of the sequence is 198.
Show that 4a+14d=994a + 14d = 994a+14d=99.
Given that the sum of the first 25 terms is 300, find the sum of the first 21 terms.
Sn S_n\,Sn is the sum of the first n n\,n terms of the sequence. Explain why the value you found in part (b) is the maximum value of SnS_nSn.
200 exam-style questions on CCEA A Level Maths 3.3 Sequences and series (A-level only), covering 3.3.1 Sequences and series (A-level only), 3.3.2 Sequences and series (A-level only), 3.3.3 Sequences and series (A-level only), 3.3.4 Sequences and series (A-level only), 3.3.5 Sequences and series (A-level only), 3.3.6 Sequences and series (A-level only), 3.3.7 Sequences and series (A-level only), and 3.3.8 Sequences and series (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.