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Date May 2015 Marks available 2 Reference code 15M.1.sl.TZ2.11
Level SL only Paper 1 Time zone TZ2
Command term Write down Question number 11 Adapted from N/A

Question

     p:x is a multiple of 12

     q:x is a multiple of 6.

Write down in words ¬p.

[1]
a.

Write down in symbolic form the compound statement

r: If x is a multiple of 12, then x is a multiple of 6.

[2]
b.

Consider the compound statement

s: If x is a multiple of 6, then x is a multiple of 12.

Identify whether s: is the inverse, the converse or the contrapositive of r.

[1]
c.

Consider the compound statement

s: If x is a multiple of 6, then x is a multiple of 12.

Determine the validity of s. Justify your decision.

[2]
d.

Markscheme

x is not a multiple of 12     (A1)     (C1)

a.

pq     (A1)(A1)(C2)

Note: Award (A1) for , (A1) for p and q in the correct order.

Accept qp.

b.

Converse     (A1) (C1)

c.

not valid     (A1)

for example 18 is a multiple of 6 and not a multiple of 12     (R1)     (C2)

 

Notes: Do not award (A1)(R0). Any multiple of 6 that is not a multiple of 12 can be accepted as a counterexample.

d.

Examiners report

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

Syllabus sections

Topic 3 - Logic, sets and probability » 3.1 » Basic concepts of symbolic logic: definition of a proposition; symbolic notation of propositions.

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