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Date	None Specimen	Marks available	2	Reference code	SPNone.2.sl.TZ0.1
Level	SL only	Paper	2	Time zone	TZ0
Command term	Find	Question number	1	Adapted from	N/A

Question

In an arithmetic series, the first term is −7 and the sum of the first 20 terms is 620.

Find the common difference.

[3]

Find the value of the 78^th term.

[2]

Markscheme

attempt to substitute into sum formula for AP M1

e.g. ${S_{20}} = \frac{{20}}{2}(2( - 7) + 19d)$ , $\frac{{20}}{2}( - 7 + {u_{20}})$

setting up correct equation using sum formula A1

e.g. $\frac{{20}}{2}(2( - 7) + 19d = 620$

$d = 4$ A1 N2

[3 marks]

correct substitution $- 7 + 77(4)$ A1

${u_{78}} = 301$ A1 N2

[2 marks]

Examiners report

[N/A]

Syllabus sections

Topic 1 - Algebra » 1.1 » Arithmetic sequences and series; sum of finite arithmetic series; geometric sequences and series; sum of finite and infinite geometric series.

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