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Date May 2022 Marks available 1 Reference code 22M.1.SL.TZ2.2
Level Standard Level Paper Paper 1 (without calculator) Time zone Time zone 2
Command term State Question number 2 Adapted from N/A

Question

The nth term of an arithmetic sequence is given by un=15-3n.

State the value of the first term, u1.

[1]
a.

Given that the nth term of this sequence is -33, find the value of n.

[2]
b.

Find the common difference, d.

[2]
c.

Markscheme

u1=12          A1

 

[1 mark]

a.

15-3n=-33           (A1)

n=16           A1

 

[2 marks]

b.

valid approach to find d          (M1)

u2-u1=9-12  OR  recognize gradient is 3  OR  attempts to solve -33=12+15d

d=-3           A1

 

[2 marks]

c.

Examiners report

A large majority of candidates earned full marks for this question. In part (a), a surprising number of candidates did not substitute n=1 into the given expression, erroneously stating u1=15. Many of these candidates were able to earn follow-through marks in later parts of the question. In part (b), algebraic errors led a few candidates to find inappropriate values for n, such as n=-6.

a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Topic 1—Number and algebra » SL 1.2—Arithmetic sequences and series
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Topic 1—Number and algebra

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