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1.4 Sequences and Series

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Question 3

A geometric series has a second term of 3 and its sum to infinity is 16.

a.

Determine the two possible values of $r$ .

[3]

b.

Determine the corresponding two possible values of $a$ .

[2]

c.

Given that $r\,$ takes the larger of the two possible values, find the smallest value of $n\,$ for which $S_n > 15.5$ .

[3]

Markscheme

1.4 Sequences and Series Questions

A Level
Maths
1.4 Sequences and Series

308 exam-style questions on OCR A Level Maths 1.4 Sequences and Series, covering 1.4.1 Binomial expansion for positive integer n, 1.4.2 Link to binomial probabilities, 1.4.3 Binomial expansion for rational n (A-level only), 1.4.4 Validity of the expansion (A-level only), 1.4.5 Sequences (A-level only), 1.4.6 Increasing, decreasing and periodic sequences (A-level only), 1.4.7 Sigma notation (A-level only), 1.4.8 Arithmetic sequences and series (A-level only), 1.4.9 Geometric sequences and series (A-level only), 1.4.10 Sum to infinity of a geometric series (A-level only), and 1.4.11 Modelling with sequences and series (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.

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