Graphs (Edexcel A Level Further Maths: Decision Maths 1)

Topic Questions

1a
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2 marks

A simply connected graph is a connected graph in which any two vertices are directly connected by at most one arc and no vertex is directly connected to itself.

Given that a simply connected graph has exactly four vertices,

(i)
write down the minimum number of arcs it can have, 

(ii)
write down the maximum number of arcs it can have.
1b
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3 marks
(i)
Draw a simply connected graph that has exactly four vertices and exactly five arcs. 
 
(ii)
State, with justification, whether your graph is Eulerian, semi-Eulerian or neither.
1c
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5 marks

By considering the orders of the vertices, explain why there is only one simply connected graph with exactly four vertices and exactly five arcs.

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2a
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1 mark

Draw the graph K5

2b
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3 marks
(i)
In the context of graph theory explain what is meant by ‘semi-Eulerian’. 

(ii)
Draw two semi-Eulerian subgraphs of K5, each having five vertices but with a different number of edges. 
2c
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2 marks

Explain why a graph with exactly five vertices with vertex orders 1, 2, 2, 3 and 4 cannot be a tree.

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3a
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2 marks

fig-1-specimen-2017-9fm0-3d

Figure 1

Define what is meant by a planar graph.

3b
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1 mark

Starting at A, find a Hamiltonian cycle for the graph in Figure 1.

3c
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4 marks

Arc AG is added to Figure 1 to create the graph shown in Figure 2.

q2-fig-2-specimen-2017-9fm0-3d

Figure 2

Taking ABCDEFGA as the Hamiltonian cycle,

use the planarity algorithm to determine whether the graph shown in Figure 2 is planar. You must make your working clear and justify your answer.

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