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Date November 2016 Marks available 2 Reference code 16N.3srg.hl.TZ0.1
Level HL only Paper Paper 3 Sets, relations and groups Time zone TZ0
Command term Write Question number 1 Adapted from N/A

Question

Let {G, } be the group of all permutations of 1, 2, 3, 4, 5, 6 under the operation of composition of permutations.

Consider the following Venn diagram, where A={1, 2, 3, 4}, B={3, 4, 5, 6}.

N16/5/MATHL/HP3/ENG/TZ0/SG/01.f

(i)     Write the permutation α=(123456346215) as a composition of disjoint cycles.

(ii)     State the order of α.

[3]
a.

(i)     Write the permutation β=(123456643512) as a composition of disjoint cycles.

(ii)     State the order of β.

[2]
b.

Write the permutation αβ as a composition of disjoint cycles.

[2]
c.

Write the permutation βα as a composition of disjoint cycles.

[2]
d.

State the order of {G, }.

[2]
e.

Find the number of permutations in {G, } which will result in A, B and AB remaining unchanged.

[2]
f.

Markscheme

(i)     (1 3 6 5)(2 4)     A1A1

(ii)     4     A1

 

Note: In (b) (c) and (d) single cycles can be omitted.

 

[3 marks]

a.

(i)     (1 6 2 4 5)(3)     A1

(ii)     5     A1

[2 marks]

b.

(123456526134)=(1 5 3 6 4)(2)    (M1)A1

[2 marks]

c.

(123456352461)=(1 3 2 5 6)(4)    (M1)A1

 

Note: Award A2A0 for (c) and (d) combined, if answers are the wrong way round.

 

[2 marks]

d.

6!=720    A2

[2 marks]

e.

any composition of the cycles (1 2), (3 4) and (5 6)     (M1)

so 23=8     A1

[2 marks]

f.

Examiners report

[N/A]
a.
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b.
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c.
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d.
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e.
[N/A]
f.

Syllabus sections

Topic 8 - Option: Sets, relations and groups » 8.10 » Permutations under composition of permutations.

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